A quenching heat treatment device, comprising a quenching tank and a control cabinet; a heating plate I for heating a quenching agent being arranged at the bottom of the quenching tank ; the quenching tank being internally provided with an internal-circulation temperature equalization device; a temperature sensor I for measuring the temperature of the quenching agent being arranged at the top of the quenching tank ; and a workpiece entrance being arranged at the top of the quenching tank ; the control cabinet being internally provided with a touch screen , an industrial control computer , a PLC controller , a temperature control module and a data acquisition board ; the industrial control computer being electrically connected with the touch screen and the PLC controller respectively via USB data lines; the PLC controller being electrically connected with the temperature control module , the data acquisition board and the internal-circulation temperature equalization device respectively; the temperature control module being electrically connected with the temperature sensor I ;, the quenching heat treatment device being characterised in that : it further comprises a sub-tank , a heating plate II for heating the quenching agent being arranged at the bottom of the sub-tank ; an external-circulation temperature equalization device for equalizing the temperature of the quenching tank and the sub-tank being arranged between the sub-tank and the quenching tank ; a temperature sensor II for measuring the temperature of the quenching agent being arranged at the top of the sub-tank ; and a cooling module for cooling the quenching agent being arranged on a side wall of the sub-tank ; a heat transfer coefficient sensor for measuring the heat transfer coefficient of the quenching agent is arranged at the top of the quenching tank , the data acquisition board being electrically connected with the heat transfer coefficient sensor ; the PLC controller is also electrically connected with the external-circulation temperature equalization device and the cooling module , and the temperature control module is electrically connected with the temperature sensor II . it further comprises a sub-tank , a heating plate II for heating the quenching agent being arranged at the bottom of the sub-tank ; an external-circulation temperature equalization device for equalizing the temperature of the quenching tank and the sub-tank being arranged between the sub-tank and the quenching tank ; a temperature sensor II for measuring the temperature of the quenching agent being arranged at the top of the sub-tank ; and a cooling module for cooling the quenching agent being arranged on a side wall of the sub-tank ; a heat transfer coefficient sensor for measuring the heat transfer coefficient of the quenching agent is arranged at the top of the quenching tank , the data acquisition board being electrically connected with the heat transfer coefficient sensor ; the PLC controller is also electrically connected with the external-circulation temperature equalization device and the cooling module , and the temperature control module is electrically connected with the temperature sensor II . <EOS>