The invention provides an SPC based motor temperature monitoring method. According to the method, an EWMA control chart model is established to monitor the motor temperature. Stable-state and unstable-state data of a motor within a period is collected and input to the model to calculate parameters in the EWMA control chart model, and process data of the motor is input to the EWMA control chart model to monitor temperature process data of the motor and further to identify and monitor temperature process drift of the motor. According to the invention, statistical theories are used, interference of random factors is eliminated, and the temperature process data of the motor is monitored and identified scientifically; due to the fact that the control chart is more sensitive to a process drift condition, a temperature drift phenomenon (namely, temperature rise) of the motor can be identified rapidly and accurately; and further, alarm prompt is provided, corresponding inspection are made, primary and secondary alarming against the motor temperature can be realized in a more reasonable manner, and motor temperature protection is more accurate, rapid and scientific.