Abstract: Based on the theory of process identification, according to the mathematical model of three-phase induction motors in αβ coordinate,the mathmatical model of the temperature forecast of the stator windings is developed. Based on 80C552 single-chip micro-processor, the hardware and software system of on-line monitoring the temperature of the stator windings of three-phase induction motors are designed.The experiments verify the correctness and feasibility of this method.