In this study, polylactic acid(PLA)-degrading bacteria were isolated and screened from the soil with PLA/PBAT film（Weifang, Shandong），using inorganic salt medium in which carbon source was the PLA. The PLA-degrading bacteria were identified by morphological observation, physiological and biochemical experiments, 16S rRNA gene sequence analysis and phylogenetic tree construction. The degrading bacteria with high protease activity, a research object, was confirmed by hydrolysis circle method. And the protease-producing conditions of the degrading bacteria was optimized by using the folinphenol reagent method and response surface methodology. Under the optimal conditions, the morphology and structure of PLA before and after degradation were analyzed by SEM, FTIR and XRD. The results showed that the PLA-degrading bacteria (Pseudomonas mendocina) was isolated and screened. After optimization, the optimal culture conditions were pH 7.4, inoculum size 1.4 mL and culture temperature 32 ℃. The highest protease activity was up to 32.15 U/mL. At the same time, the protease of PLA-degrading bacteria could catalyzed the ester bond in the degradation material. The degradation rate of PLA could reach 29.35% within 5 days.