Fibrous NPAN was synthesized by the method of protic acid doping with NAN containing carboxyl. A series of NPAN/Ag/Ag₃PO₄ composites with different NPAN content were prepared by in situ polymerization of silver phosphate on the surface of NPAN. By means of FT-IR, XPS, Raman, TEM, TG and PL, the structure and morphology of the material were analyzed, and the photocatalytic performance of the material was studied. The results showed that the degradation efficiency of 10wt% NPAN/Ag/Ag₃PO₄ composite for RhB dye was the highest, reaching 97.635%. After five cycles, the photocatalytic degradation efficiency of RhB dye could still reach 93.6%, while the degradation efficiency of silver phosphate decreased from 83.2% to 54.12%. The introduction of NPAN could accelerate the separation of photogenerated electron holes, enhance the structural stability of the composite material, and improve the photocatalytic effect and cyclic stability of the composite material. Finally, the catalytic mechanism was explored through the capture experiment of active substance, and it was proved that the main sources of catalytic activity were photogenerated holes and strong oxidation of·O₂^-.