Abstract: The effects of time, temperature and medium contacted on the migration of epoxidized soybean oil (ESO) in plasticized poly(vinyl chloride) (PVC) were determined. The diffusion coefficient of ESO and its blends with the plasticizer tri(2 ethylhexyl) trimellitate (TOTM) at 120 ℃ were calculated. The results showed that an “induction period” appeared at low temperature which reduced upon increasing the temperature. The whole migration stage was in the induction period for ESO at 40 ℃, without any mass loss within 96 h. The induction period of migration was shorter than 6 h at 80 ℃. At 120 ℃, ESO migrated to active carbon, PVC podwer and other media, and the “induction period” disappeared. The linear fitting of diffusion coefficient at 120 ℃ showed that the migration of ESO into various medias other than PVC particles were followed the Fick’s law. Moreover, the amount of migration of plasticizer reduced when the content of ESO in the ESO/TOTM blends increased.