Theranostic nanomedicine is emerging as a promising therapeutic paradigm, combining imaging and therapeutic functions in a single agent. This review focuses on the construction strategies and challenges of nanoparticle-based theranostic agents, organized by the core materials of the nanoplatforms. Iron oxide nanoparticles (IONPs), quantum dots (QDs), carbon nanotubes (CNTs), gold nanoparticles (Au NPs), and silica nanoparticles (SiO2 NPs) are discussed in detail. IONPs, with their superior magnetic properties and biocompatibility, are widely used in MRI contrast agents and can be easily coupled with drugs or genes. QDs, known for their unique optical properties, have been explored for drug delivery and gene therapy but face challenges due to their innate toxicity. Au NPs, with their strong surface plasmon resonance, are effective in photothermal therapy and gene delivery. CNTs, despite their non-biodegradability, show promise in drug delivery and photothermal therapy. SiO2 NPs, a safe material, provide a versatile platform for loading various imaging and therapeutic functions. The review highlights the progress and potential of these nanoplatforms in theranostic applications, emphasizing the need for further research to address challenges such as toxicity and surface coating techniques.Theranostic nanomedicine is emerging as a promising therapeutic paradigm, combining imaging and therapeutic functions in a single agent. This review focuses on the construction strategies and challenges of nanoparticle-based theranostic agents, organized by the core materials of the nanoplatforms. Iron oxide nanoparticles (IONPs), quantum dots (QDs), carbon nanotubes (CNTs), gold nanoparticles (Au NPs), and silica nanoparticles (SiO2 NPs) are discussed in detail. IONPs, with their superior magnetic properties and biocompatibility, are widely used in MRI contrast agents and can be easily coupled with drugs or genes. QDs, known for their unique optical properties, have been explored for drug delivery and gene therapy but face challenges due to their innate toxicity. Au NPs, with their strong surface plasmon resonance, are effective in photothermal therapy and gene delivery. CNTs, despite their non-biodegradability, show promise in drug delivery and photothermal therapy. SiO2 NPs, a safe material, provide a versatile platform for loading various imaging and therapeutic functions. The review highlights the progress and potential of these nanoplatforms in theranostic applications, emphasizing the need for further research to address challenges such as toxicity and surface coating techniques.