The invention relates to a composite material of light-degradation antibiotic polylactic acid, which mainly comprises polylactic acid and nanometer TiO2, wherein, the content of polylactic acid is 90.0% to 99.0%, the content of nanometer TiO2 is 1.0%to 10.0%. The process for preparation comprises adding coupling agent to flow back for 2-4 hors under the temperature of 80 DEG C+-10 DEG C after dispersing nanometer TiO2 in methyl ethyl ketone, acetone or triethylamine disperser in ultrasonic, placing in a straight sealing tube with lactide after whizzing and drying, adding accelerating agent, and preparing in 150 DEG C +- 10 DEGC vacuum to polymerize for 2-4 hours. Compared with polylactic acid, the heat decomposition temperature, the glass transformation temperature and mechanical properties of the invention are all greatly improved, and the invention has the functions of antibacterial activity and ultraviolet absorption, the degradation rate is obviously accelerated under the radiation of ultraviolet light and natural conditions, and the invention has complete biodegradability. The composite material of light-degradation antibiotic polylactic acid of the invention adopts an in-situ polymerization, whose processing technology is simple, production cost is low, and application prospect is wide.