The invention provides a method and a device for carrying out isothermal normalizing heat treatment on alloy cemented steel parts utilizing forging waste heat. The method comprises the following steps: after finish forging of a forged steel blank, slowly cooling the forged steel blank from the final forging temperature to a pre-cooling temperature T1 at a pre-cooling rate V1, insulating heat for t1, then rapidly cooling to a forced cooling temperature T2 at a forced cooling rate V2, carrying out isothermic transition at the isothermic temperature of Tiso for isothermic time tiso, and then cooling to room temperature in a random cooling mode. The invention also provides a device for isothermal normalizing of cemented steel parts utilizing forging waste heat, and the device is composed of atransmission mechanism, a slow cooling chamber, a rapid cooling chamber, an isothermal furnace, a control system, a transmission system and process parameter calculation and correction software. The calculated process parameters can be used for precise control and operation of the device, thereby guaranteeing that the normalizing quality of steel parts is superior or at least equal to the heat treatment quality using conventional normalizing and isothermal normalizing.