Abstract: The soybean oil based polyester was synthesized by the polycondensation of o-phthalic anhydride and the soybean oil monoglyceride obtained from the transesterification of soybean oil and glycerol at 230-240 ℃. The soybean oil polyester was characterized by gel permeation chromatography (GPC) and FT-IR. And the synthesized soybean oil polyester was then blend with polyvinyl chloride(PVC)to form a plasticized PVC. Thermodynamic properties, plasticizer migration stability and mechanical properties of soybean oil polyester plasticized PVC were investigated. The results showed that relative molecular mass of the polyester was 3 541. The thermal degradation temperature of the plasticized PVC was 256.1 ℃. And tensile strength and elongation at break for this plasticized PVC could reach 6.5 MPa and 230.3%, respectively. In addition, the combination of soybean oil polyester and dioctyl phthalate(DOP) using as complex plasticizer to plasticize PVC was also evaluated. The migration ratio of these complex plasticizers in distilled water, acetic acid solution, ethanol solution, petroleum ether and olive oil reduced to 0.18%,0.22%,0.28%,0.83% and 0.34%, which was indicative of their excellent migration property. Herein, the thermal and mechanical properties of the soybean oil polyester plasticized PVC could maintain for long time and the potential harm to human caused by plasticizer could be reduced at same time.