The invention provides a constant temperature device required in a battery charge-discharge testing process, and belongs to the technical field of batteries. The constant temperature device comprises a tank body, a temperature controller, a thermoelectric semiconductor refrigeration assembly, a cooling fan, a thermocouple, a dehumidifier, a battery clamp and a power supply power source. The tank body has the heat preservation effect. A front cover plate capable of being opened is arranged on the front side of the tank body, the thermocouple, the cooling fan, the thermoelectric semiconductor refrigeration assembly, the dehumidifier and the battery clamp are arranged in the tank body, the temperature controller is arranged at the top of the outer side of the tank body, and the temperature controller is simultaneously connected with the thermocouple, the thermoelectric semiconductor refrigeration assembly and the cooling fan through holes in the tank body to achieve control over temperature rise and temperature drop. The constant temperature device has the advantages of being easy to operate, practical, convenient to maintain and low in cost, and the constant temperature device is suitable for battery charge-discharge testing.