Among the raw materials of biodegradable plastic bags, polylactic acid (PLA) is known as one of the most promising varieties, and has biocompatibility, biodegradability and resource regeneration. In the natural environment, PLA waste can be degraded (6-12 months) through hydrolysis and a series of biological metabolic processes into CO2 and H2O. These CO2 and H2O can be used by plants to photosynthesize to produce starch and produce Starch can be reused for the production of polylactic acid. Therefore, polylactic acid is not only an inexhaustible material, but also can reduce white pollution and save petroleum resources. It is a kind of natural carbon balance Materials, so the application and promotion of biodegradable plastic bags is also energy saving and emission reduction, reducing pollution.