PPC(Polypropylene carbonate) was made from carbon dioxide which is mam gas to cause global warming. PPC is known as a biodegradable polymer. However, the weak thermal property has been an obstacle to develop various applications. In this work, we studied PPC's compatibility with Polycarbonate(PC) and Poly-L-Lactic Acid(PLLA) in order to improve the thermal properties and processability of PPC. The compatibility of blends was investigated by DSC(Differential Scanning Calorimetry) and DMA(Dynamic Mechanical Analyzer). As a result, we could find the composition of 75/25 in PPC/PLLA blends is a miscible system showing Low Critical Solution Temperature(LCST) behavior.