The grinding hardening is a new technology in which thermal of grinding zone is utilized to heat-treat the workpiece surface layer. In grinding hardening process, grinding zone temperature directly affects the quality of surface layer of heat treatment. The high temperature heat pipe is a very good device of control heat transfer. In order to make the grinding zone temperature slightly change in grinding process, a temperature automatic control system was designed. A high temperature heat pipe was contacted with the workpiece’s grinding zone. The zone temperature was measured using infrared radiation pyrometer and the temperature data were used to control the high temperature heat pipe’s thermal resistance through PID controller,which was used to adjust the contact area between workpiece and high temperature heat pipe. Thus control requirements of workpiece’s surface hardening are achieved.