The aim of this study was to prepare composite antibacterial materials using PLA and chitosan. The biodegradable materials were first prepared by hot-melt extrusion, and then the influence of the percentages of chitosan was researched through the test of mechanical property and antibacterial property. With the increase of the chitosan content, the tensile strength and bending strength of the composite materials showed a slightly decreasing trend, the impact resistance at the fracture was substantially unaffected and the elongation at break showed a downward trend after initial rise. When 4.0% mass fraction of chitosan was added, the composite material had the best comprehensive mechanical property. When 8.0% mass fraction of chitosan was added, the composite material showed obvious antibacterial activity. The biodegradable composite made from polylactic acid and chitosan has broad prospects, we need to further explore the relationship between the two materials to prepare a more excellent biodegradable composite.