Prussian blue analogs (PBAs) are promising electrode materials for capacitive deionization (CDI) due to their unique 3D framework structure. However, their practical applications are limited by low desalination capacity and poor cyclic stability. This study introduces an entropy engineering strategy by incorporating high-entropy (HE) concepts into PBAs to address these issues. By introducing five or more metals sharing N coordination sites, a high-entropy hexacyanoferrate (HE-HCF) is constructed, increasing the configurational entropy of the system to above 1.5R. The HE-HCF demonstrates excellent cycling performance with a capacity retention rate of over 97% after 350 ultralong-life cycles and a high desalination capacity of 77.24 mg g⁻¹ at 1.2 V. Structural characterization and theoretical calculations reveal that the high configurational entropy helps restrain phase transitions, strengthen structural stability, and optimize Na⁺ ion diffusion, leading to improved performance. This research provides a new approach for designing electrodes with high performance, low cost, and long-lasting durability for CDI applications.Prussian blue analogs (PBAs) are promising electrode materials for capacitive deionization (CDI) due to their unique 3D framework structure. However, their practical applications are limited by low desalination capacity and poor cyclic stability. This study introduces an entropy engineering strategy by incorporating high-entropy (HE) concepts into PBAs to address these issues. By introducing five or more metals sharing N coordination sites, a high-entropy hexacyanoferrate (HE-HCF) is constructed, increasing the configurational entropy of the system to above 1.5R. The HE-HCF demonstrates excellent cycling performance with a capacity retention rate of over 97% after 350 ultralong-life cycles and a high desalination capacity of 77.24 mg g⁻¹ at 1.2 V. Structural characterization and theoretical calculations reveal that the high configurational entropy helps restrain phase transitions, strengthen structural stability, and optimize Na⁺ ion diffusion, leading to improved performance. This research provides a new approach for designing electrodes with high performance, low cost, and long-lasting durability for CDI applications.