The invention discloses a remote adjusting device of hot water temperature of a gas water heater; and the remote adjusting device consists of a first flow measuring unit, a second flow measuring unit, an adder circuit unit, a scale value calculating unit, a flow threshold switch unit and a proportional valve driving unit. The gas water heater includes a first hot water outlet and a second hot water outlet; the hot water temperature is changed by using a method of remotely controlling two ways of hot water flows through a water valve; when the hot water flow of the first hot water outlet is relatively increased, the combustion power of the gas water heater is increased, and the hot water temperature rises; and when the hot water flow of the first hot water outlet is relatively decreased, the combustion power of the gas water heater is reduced, and the hot water temperature is lowered. The device needs no wire or wireless remote controller, can realize remote adjustment of hot water temperature of the gas water heater, and is stable and reliable in control result.