Abstract: Aiming at the problem that excess temperature of windings affects insulating property in running of motor,the paper designed a new thermal protector with single-chip microcomputer based on fuzzy control.Through analyzing and discussing different standards and models of thermal over-loading,the paper put forward an optimal model of thermal characteristic for thermal protector with single-chip(microcomputer),namely exponential model of heating and cooling and its modeling mechanism.For the(inaccurate) problem of the selected delay time of the thermal protector,the paper also designed a set of(software) of the thermal protector with the theory of fuzzy control,which improved the action precision and(reliability) of the thermal protector.