Provided is a fully-digital constant-temperature water cooling control system for a high-pressure high-capacity IEGT converter. The fully-digital constant-temperature water cooling control system mainly comprises a cooling water circulation system, which is composed of a liquid storage tank, an IEGT converter water cooling system in an IEGT converter, a water pump for driving circulation of the cooling water in the IEGT converter water cooling system and a motor thereof. The fully-digital constant-temperature water cooling control system also comprises a temperature transmitter and a constant-temperature cooling control cabinet. The temperature transmitter is disposed at a water outlet pipe of the IEGT converter water cooling system to detect the temperature of the cooling water in the water outlet pipe of the IEGT converter water cooling system and output a temperature signal to the constant-temperature cooling control cabinet. The constant-temperature cooling control cabinet outputs a rotating-speed control signal to the motor of the water pump according to the received temperature signal, so as to adjust the rotating speed of the motor and therefore to control the flow of the cooling water in the cooling water circulation system. According to the utility model, the rotating speed of the motor of the water pump is controlled according to the temperature of the cooling water flowing out from the converter, so as to control the flow of the cooling water, so that the converter continuously works at the constant temperature. In addition, backflow of excess cooling liquid is prevented, thereby significantly saving the energy.