The invention discloses an intelligent constant-temperature solar water heating system with an automatic water replenishing function. The intelligent constant-temperature solar water heating system comprises a heat collecting plate internally provided with a working medium, a water storage tank and a controller, the water storage tank is internally provided with a heat exchanger and an electric heater, a circulation pump is arranged in a heating pipeline communicating the heat collecting plate and the heat exchanger, and a cold water input pipeline of the water storage tank is provided with anelectromagnetic proportional valve, a flow sensor and a temperature sensor; and when the water level of the water storage tank is lower than the critical low water level due to the fact that a user uses water, the controller controls the electromagnetic proportional valve to automatically replenish water, the electric heater is stared, and the opening degree of the electromagnetic proportional valve is adjusted based on the temperature of cold water, the water temperature of the water storage tank and the flow value of the flow sensor so as to make the heat quantity required by rising of thetemperature of the replenished cold water to the water temperature of the water storage tank be equal to the heat quantity generated by the electric heater in the corresponding period. In the replenishing process of the cold water, the water temperature of the water storage tank is made to keep constant, the user does not need to frequently adjust the ratio of the cold water to hot water in the process of using water, and water using is very convenient, and finishing of one-time water using process by the user is more conducive.