Objective：This study aims to investigate the antibacterial function of biodegradable magnesium(Mg) reinforced polylactic acid(PLA)composite membranes. Methods：In the present study，Mg/PLA composite membranes were prepared by loading different proportions of Mg particles into PLA matrix for guided bone regeneration(GBR). The surface morphology of samples were observed by scanning electron microscope，and the mechanical performance of the composites was detected by the electro⁃mechanical universal testing machines. We immersed the material in phosphate buffered saline(PBS)and detected the pH variation during the degradation of 24 h. MC3T3⁃E1 cell line，L929 cell line were used to detect biocompatibility of the material degradation product by CCK⁃8 method. Besides，we observe the growth of E.coli and S.aureus on the surface of material with scanning electron microscopy and bacterial plate counting. Results：Results showed that 10% wt and 20% wt of Mg ehanced the mechanical strength of the material， however，the high Mg content(40%wt)weekened the enhancement effect of Mg particles on the mechanical properties of PLA. The degradation products of PLA or any of the composites showed good biocompatibility. And 20% wt Mg/PLA and 40% wt Mg/PLA composite membranes had obvious antibacterial functions，and the antibacterial rate increased with the increase of Mg content. Conclusion：Mg/PLA composite material has a good improvement on the mechanical properties and antibacterial effect of polymer，expecting to be used as a barrier membrane material for GBR.