Abstract: The kinetics of the enzymatic degradation of PLA is investigated by quartz crystal microbalance (QCM). There are several important factors which affect the enzymatic degradation of PLA by proteinase K. The enzymatic degradation of PLA by proteinase K is a twostep process. The first step is adsorption of the enzyme on the surface of the substrate and the second step is degradation of PLA by proteinase K. The initial degradation rate increases with the increasing enzyme concentration and attains to be constant after the enzyme concentration approaches a certain value. The initial degradation rate increases with the increasing pH in the range of pH from 7 to 9. The initial degradation rate increases with increasing temperature in the range of temperature from 25 ℃ to 40 ℃.