Digital light processing (DLP) based multimaterial 3D printing has shown great potential in various applications, including metamaterials, flexible electronics, biomedical devices, and robotics. This technology can seamlessly integrate distinct materials into one printed structure. DLP MM 3D printing is compatible with a wide range of materials, from hydrogels to ceramics, and can print high-resolution, high-complexity, and fast-speed MM 3D structures. This paper introduces the fundamental mechanisms of DLP 3D printing and reviews recent advances in DLP MM 3D printing technologies, focusing on material switching methods and material contamination issues. It summarizes typical examples of DLP MM 3D printing systems developed in the past decade, including their system structures, working principles, material switching methods, residual resin removal methods, printing steps, and representative structures and applications. The paper also provides perspectives on the future development of DLP MM 3D printing technology. DLP 3D printing is based on photopolymerization, which involves four steps: photodecomposition, initiation, propagation, and termination. The essence of DLP 3D printing is the photopolymerization reaction, which is typically modeled using first-order reaction equations. The UV light intensity distribution in the resin is modeled using the Beer-Lambert law. The DLP projector generates UV light patterns, which are modulated by the digital micromirror device (DMD) chip. The intensity of a UV pattern is the summation of the light intensity from each pixel, following a Gaussian distribution. The main challenges in DLP MM 3D printing include material contamination during the switching process. Two major methods of MM switching are vat switching and resin switching. Vat switching involves multiple resin vats, while resin switching uses a single resin vat with a fluidic system to switch resins. The material contamination issue is more severe in vat switching, but the resin switching method leads to more resin waste. To address this, researchers have proposed various methods to remove residual resin, including washing and drying, wiping, air jetting, and spinning. The spinning method, which uses centrifugal force, is particularly effective for removing residual resin and allows the fabrication of large-area MM 3D structures. DLP MM 3D printing systems have been developed using various material switching methods. The top-down MMSL system uses vat switching and includes a deep-dip coating strategy to avoid contamination. The resin switching method can be applied to both top-down and bottom-up DLP systems, allowing the fabrication of MM 3D structures. However, the resin switching method leads to substantial resin waste. The bottom-up DLP MM 3D printing system with vat switching can print larger area MM 3D structures and has less constraints on the viscosity of the material resin. This system has been intensively explored in terms of vat delivery approaches, residual resin removal, and application explorations. The two-stage cleaningDigital light processing (DLP) based multimaterial 3D printing has shown great potential in various applications, including metamaterials, flexible electronics, biomedical devices, and robotics. This technology can seamlessly integrate distinct materials into one printed structure. DLP MM 3D printing is compatible with a wide range of materials, from hydrogels to ceramics, and can print high-resolution, high-complexity, and fast-speed MM 3D structures. This paper introduces the fundamental mechanisms of DLP 3D printing and reviews recent advances in DLP MM 3D printing technologies, focusing on material switching methods and material contamination issues. It summarizes typical examples of DLP MM 3D printing systems developed in the past decade, including their system structures, working principles, material switching methods, residual resin removal methods, printing steps, and representative structures and applications. The paper also provides perspectives on the future development of DLP MM 3D printing technology. DLP 3D printing is based on photopolymerization, which involves four steps: photodecomposition, initiation, propagation, and termination. The essence of DLP 3D printing is the photopolymerization reaction, which is typically modeled using first-order reaction equations. The UV light intensity distribution in the resin is modeled using the Beer-Lambert law. The DLP projector generates UV light patterns, which are modulated by the digital micromirror device (DMD) chip. The intensity of a UV pattern is the summation of the light intensity from each pixel, following a Gaussian distribution. The main challenges in DLP MM 3D printing include material contamination during the switching process. Two major methods of MM switching are vat switching and resin switching. Vat switching involves multiple resin vats, while resin switching uses a single resin vat with a fluidic system to switch resins. The material contamination issue is more severe in vat switching, but the resin switching method leads to more resin waste. To address this, researchers have proposed various methods to remove residual resin, including washing and drying, wiping, air jetting, and spinning. The spinning method, which uses centrifugal force, is particularly effective for removing residual resin and allows the fabrication of large-area MM 3D structures. DLP MM 3D printing systems have been developed using various material switching methods. The top-down MMSL system uses vat switching and includes a deep-dip coating strategy to avoid contamination. The resin switching method can be applied to both top-down and bottom-up DLP systems, allowing the fabrication of MM 3D structures. However, the resin switching method leads to substantial resin waste. The bottom-up DLP MM 3D printing system with vat switching can print larger area MM 3D structures and has less constraints on the viscosity of the material resin. This system has been intensively explored in terms of vat delivery approaches, residual resin removal, and application explorations. The two-stage cleaning