The novel antimicrobial and biodegradable composite nanofiber membranes were successfully fabricated by electrospinning of polyvinyl alcohol (PVA) solution with dispersed graphitic carbon nitride (g-C3N4) nanosheets followed with crosslinking reaction. The morphology, physical and antimicrobial properties of PVA/g-C3N4（P-CN）composite nanofiber membranes were systematically characterized. The effects of different g-C3N4 concentrations on the morphology and performance of the composite nanofiber membranes were investigated. The SEM results show that the diameter of P-CN fiber is between 200~300 nm. After crosslinking, the fiber diameter becomes about 1 μm. g-C3N4 nanosheets are evenly distributed on the surface of the nanofibers with the content below 3%. At the same time, the tensile and swelling tests reveal that the cross-linked composite nanofiber membranes have good mechanical properties and excellent swelling resistance. The antibacterial test results show that the antibacterial effect of the composite nanofiber membranes on E. coli and S. aureus is significantly increased with the increase of g-C3N4 content, the maximum antibacterial radius could reach 10 mm under the visible light excitation of 4×104 Lux for 10 min in advance. P-CN-5 composite nanofiber membranes demonstrate excellent antimicrobial performance with a small amount of g-C3N4, which should provide great potential for applications such as antimicrobial coatings and packaging.