Abstract: This paper reported an investigation on the degradation properties of poly(propylene carbonate) (PPC)/poly(lactic acid) (PLA) blends in a marine environment. The mechanical properties, surface microstructure, chemical structure, weight loss, thermal properties and crystalline properties of the blends were evaluated by means of mechanical measurements, scanning electron microscope, attenuated total reflection infrared spectroscopy. The results indicated that the tensile strength of the blends at the PPC/PLA mass ratio of 10/90, 30/70, 50/50 and 70/30 increased continuously with an increase of degradation period, and however their elongation at break decreased drastically after a degradation period of 30 days and then kept a stable value. There were clear pores and defects found on the surface of pure PPC and PLA resins after they were placed in a marine environment for 240 days, whereas the blends at a PPC/PLA mass ratio of 50/50 did not exhibit any pores and defects. Both pure PPC and pure PLA exhibited an increasing trend in hydroxyl index, carbonyl index and lactic acid index, and such a trend become more significant at the first 30-day degradation period, whereas the blends at a PPC/PLA mass ratio of 50/50 showed no change. The weight loss of the blends mainly took place at the first 30-day degradation period, which resulted in a weight loss rate of less than 10 wt %, indicating the degradation of blends was not significant. Moreover, the blends showed an increase in characteristic temperature at a weight loss of 5 wt %, whereas their characteristic temperature at the maximum weight-loss rate did not change any more.