Based on COMPASS forcefield, the relationship between microstructure and macroscopic properties of poly (propylene-co-γ-butyrolactone carbonate) (PPCG) was firstly investigated with ‘Materials Studio’ simulation soft successfully. The results of simulation showed that the molecular chain of PPCG was flexible. Degradable carbonic and carboxylic ester groups were distributed outside the PPCG cell. Furthermore the structure of micro-phase separation was observed in PPCG cell. The structure of micro-phase separation of PPCG can be applied to the self-assembly of drug molecule.