A preparation method of vegetable oil polyol, which is obtains by carrying out allylic oxidation treatment of vegetable oil, increasing the content of hydroxyl group in the product and then one step reaction between epoxidation and ring-opening. At the same time, the present invention also discloses novel vegetable oil polyol made by the preparation method and the application of the vegetable oil polyol in preparation of polyurethane foam material. Compared with the prior art, the method has the advantages of simple operation, low energy consumption and low side reaction occurrence rate.