The invention discloses a method for controlling the temperature of engine coolant, and aims to achieve the purpose. According to the technical scheme, the method for controlling the temperature of the engine coolant comprises the following steps: step 1, carrying out automatic system checking; step 2, acquiring an engine rotating speed signal, an engine load signal, an exhaust air-fuel ratio signal, an intake air temperature signal, a water temperature signal, a vehicle speed signal and an engine knocking signal in real time; step 3, establishing an exhaust temperature model and an engine knocking model; step 4, calculating the exhaust temperature condition of an engine in real time by the exhaust temperature model, and calculating the condition of an engine knocking receding angle by theengine knocking model; and step 5, outputting a control signal to an electronic thermostat according to calculated results. By the method, direct relation between the temperature of the coolant and the combustion state of the engine can be established, accurate control is implemented, the fuel economy is low, meanwhile, the temperature of the engine is prevented from being over high, parts of theengine are protected, and the electronic thermostat controls water temperature efficiently, accurately and stably.