The invention discloses a control signal calculation circuit for a proportional gas adjustment valve of a gas water heater. The gas water heater comprises a first hot water outlet port, a second hot water outlet port, a cold water inlet port, a relay gas switch and the proportional gas adjustment valve. The outlet hot water flow rate of the first hot water outlet port and the total inlet cold water flow rate of the cold water inlet port are detected, and the ratio of the outlet hot water flow rate of the first hot water outlet port to the total inlet cold water flow rate of the cold water inlet port is calculated by the control signal calculation circuit for the proportional gas adjustment valve and comprising an ADC and a DAC to obtain a proportional value control voltage; when the proportional value control voltage is increased, the opening degree of the proportional gas adjustment valve is controlled to be increased, and the combustion power of the gas water heater is increased; andwhen the proportional value control voltage is reduced, the opening degree of the proportional gas adjustment valve is controlled to be reduced, and the combustion power of the gas water heater is reduced. According to the method, a wired remote controller or a wireless remote controller is not needed, remote adjustment for a hot water temperature of the gas water heater can be realized, and a stable and reliable control result is achieved.