Poly(butylene succinate-co-terephthalate)(PBST) was synthesized and molecular weight and thermal properties were investigated. There was 10$0^{circ}C$ change in the melting and crystallization temperatures of PBST with composition. As a result of manufacturing the produced polymer into film and conducting a decomposition experiment, it was observed that the film of S/T=1 and 2 composition ratio were decomposed by lipase PS. Moreover, after 42 days, 9 and 40% weight reduction was observed, respectively. However, since there was no change in the weight-average molecular weight, it appears that decomposition advances from the surface of the film.