The effect of polydopamine coating on improving photostability of polyphenylene sulfide (PPS) fiber was investigated in detail. Due to strong adhesion ability and self-polymerization of dopamine in alkaline solution, the polydopamine could be easily coated on polyphenylene sulfide fiber under mild conditions. XPS, ATR-FTIR and SEM, which indicated the polydopamine coating was homogeneous, confirmed the polydopamine coating on PPS fiber. The UV-spectra analysis of polydopamine coating showed that it had a strong absorbance in ultraviolet wavelength and was very stable to it, which implied that the polydopamine was a potential photoprotection agent. 2,2-Diphenyl-1-picrylhydrazyl (DPPH) experiment further revealed that the PDA could quench free radicals, suggesting PDA was a good antioxidant. This scavenging ability of PDA might contribute to improving photostability of PPS fiber. Compared to pristine PPS fiber, the PPS fiber coated by polydopamine obviously had better photostability after ultraviolet irradiation according to mechanical test, which proved that polydopamine coating did improve the photostability of PPS fiber.