The invention particularly relates to a slag powder grinding control system. The slag powder grinding control system comprises a belt conveyor, a slag cabin, a fuel gas hot blast heater, a vertical mill motor, a vertical roller mill, a slag separator, a returned material elevator, a dust remover, a vertical mill exhaust blower, a pipeline chimney, a chute, a storage elevator, a frequency converter, a PLC controller, a water tank and a plurality of finished product warehouses. According to the control system disclosed by the invention, in the slag powder grinding process, the ground mineral powder material is blown up by jet stream of hot-blast air generated by the fuel gas hot blast heater; the slag is fractionated by the slag separator according to the particle size and fineness requirements on the mineral powder material, so that the efficiency of grinding the mineral powder into fine powder is improved; the whole control system is reasonable in design, high in yield and high in production safety; the slag powder grinding control system is compact in structure, small in occupied area and high in production safety, and has the effects of saving energy and being efficient.