The invention discloses a low alloy steel production method which is characterized in that the method comprises the following steps: 1) treatment in a converter, to be more specific, desulphurized molten steel is added into a steelmaking converter, under oxygen supply condition, a slagging material is added for steelmaking slagging, when the molten steel temperature reaches 1650 to 1700 DEG C, oxygen supply is stopped, argon is combinedly blew for stirring, and after combined blowing argon for stirring, the slag is pushed off to discharge steel to obtain first molten steel; 2) RH vacuum treatment, to be more specific, the first molten steel enters into a RH processing working station for vacuum supply and gas flow improvement, then under vacuum condition, first batch carbon powder, an aluminum pill deoxidizer, an alloying material and second batch carbon powder are successively added into the first molten steel, and second molten steel is obtained by vacuum treatment; and 3) continuous casting processing, to be more specific, the second molten steel is continuously casted. The low alloy steel production method can greatly reduce low alloy steel production cost, and significantly improve the purity of molten steel.