Production method of steel for petroleum valve body

The invention relates to a production method of steel for a petroleum valve body, which comprises the steps of molten iron pretreatment, converter steelmaking, LF (ladle furnace) refining, VD (vacuum degassing), continuous casting, slow cooling, forging and heat treatment to obtain the steel for the petroleum valve body. A slag system used in the LF refining comprises the following components in percentage by mass: 48 to 52 percent of CaO, 3 to 6 percent of SiO2, 37 to 42 percent of Al2O3 and the balance of MgO. According to the production method provided by the invention, a specific slag system is introduced in the LF refining stage, so that the levels of B-class, D-class and Ds-class inclusions in the obtained petroleum valve body steel product are reduced, and the service life of the product is prolonged.