The invention relates to the technical field of oil pumps, discloses a pressure relief device of an oil pump and relates to a body of an oil pump. The pressure relief device comprises a pressure relief valve, a pressure limiting spring, a steel ball and a steel ball seat. One end of the pressure limiting spring is connected with the pressure relief valve, the other end of the pressure limiting spring is connected with the steel ball, and the steel ball seat is matched with the steel ball, is mounted in a pressure relief hole of a body of the oil pump and is connected with the steel ball. The pressure relief device has the advantages that the steel ball seat is additionally arranged in the pressure relief hole on a principle that the basic structure of the pressure relief valve is unchanged, accordingly, the abrasion resistance of the steel ball and the pump body can be enhanced, the service life of the oil pump can be prolonged, and the sealing performance of the oil pump can be improved.