Abstract: The degradation rate and the change of molecular weight of polyblends PET/PLA with different ratios prepared by solution blends were investigated.The degradation rate of the membrane of PET/PLA（9∶1）was the highest among the four polyblends.The highest degradation rate of the polyblend membranes was observed in basic buffer solutions.The change of molecular weight of PET in polyblends under natural condition was similar to the change of the degradation rate of polyblends under all degradation conditions.