The FEM simulation is used to study the intermediate frequency induced heating process. The temperature distributions and temperature differences are obtained by two kind frequencies of 500 and 1000Hz. It is found that, in this simulation condition, the length of uniform temperature region is about three times of the coil height. It is obvious that, no matter which frequency, the heating rate is very high. With the process of 1000Hz, in less than 20 seconds, the heating temperature can reach a reasonable temperature, and with a process of 500Hz, the temperature can reach a reasonable temperature in more than 40 seconds. It is recommended that the frequency between 500 to 1000Hz could be available for a practical use.