Abstract: Magnesium alloy implants are a kind of biodegradable implant materials. Due to their elastic modulus similar to that of human bone, they have broad prospects for clinical application. However, after degradation in the human body, magnesium alloys lead to the formation of a hydrogen-rich alkaline environment, which causes chronic inflammation and increases the risk of bacterial infection, thus limiting their practical application.To address the above problems, a magnesium fluoride-polyvinyl alcohol-chitosan-copper nanoparticle composite coating (FPC coating) was fabricated on the surface of AZ31B magnesium alloy in this work. A MgF₂ underlayer was prepared by grinding, acid pickling and fluoridation, and a polyvinyl alcohol-chitosan top layer containing copper nanoparticles was loaded via spin-coating. The microstructure, composition and basic physicochemical properties of the coating were systematically characterized, and its corrosion resistance, antibacterial property, blood compatibility and in vivo biocompatibility were investigated.The results showed that a dense MgF₂ coating was formed on the polished magnesium alloy surface, and the corrosion resistance was significantly improved. The FPC coating exhibited excellent corrosion resistance: the corrosion current density was reduced by approximately three orders of magnitude compared with the bare magnesium alloy, and the protection efficiency reached 99.81%. The FPC coating achieved stable antibacterial activity through the sustained release of Cu²⁺, and simultaneously possessed good blood compatibility and biocompatibility. This composite coating provides a feasible strategy for the surface functionalization of biodegradable magnesium alloy implants.