At present，the industrial application of per-acid to the production of epoxidized soybean oil ( ESO) can lead to serious pollution，so it is necessary to explore the preparation technologies of green epxidized soybean oil． In the investigation，by taking H2O2 as the oxygen source，a mathematical model on the basis of the response surface methodology was constructed to optimize the preparation technology of ESO obtained through phase-transfer catalysis． Then，the prepared ESO was characterized by means of FT-IＲ，and its physical and chemical property and thermal stability were also analyzed． The results show that，under the optimal conditions，namely，a mass ratio of H2O2，catalyst，PEG and soybean oil of 87∶29∶30∶100，a temperature of 55℃ and a reaction time of 3. 5 h， the predicated epoxy value of ESO，which is 6. 48% ，is close to the tested value of 6. 40% ，which means that the proposed model on the basis of the response surface methodology can be used to guide the preparation of ESO． The prepared ESO with mild reaction conditions and short reaction time meets the national industry standard，and it is of a better thermal stability，specifically，its epoxy value decreases only by 0. 48% with a processing time of 3. 0 h at 177℃ ． The results of IＲ confirm that the unsaturated double bonds are converted into the epoxy bonds after the selective oxidation of soybean oil．