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This study introduces the mechanical structure and control system of an electric water pump(EWP).Based on this EWP,multiple tests have been done to analyze the vehicle warm-up process.The results show that coolant temperature in engine warm-up process experiences three stages rising from normal condition to 95℃.The 1st stage begins with the engine starting and ends up with the thermostat opening: EWP flow has little influence on the rising of coolant temperature,but On-Off mode combing with a fitting strat-egy could reduce time by 23%~25%in this stage.During the 2nd stage,coolant in the radiator and the bypass system start to mix due to the temperature difference.Increasing the flow of EWP could accelerate the process.Once the coolant temperature of inner engine is equal to outer radiator,the 3rd stage begins,and EWP should decrease the flow to reduce the heat loss and speed up the coolant temperature rising.