Abstract: Main drive internal gear bearing is a key component of large shield boring machine, More than 95% of the parts of the large shield boring machine in China have been independently developed, almost depends on imports.The gear modulus of the main drive bearing with high load bearing, high reliability of the large shield boring machine is larger, for which, the hardness and the depth of the hardening layer of the induction quenching on tooth put forward higher technical requirements. This paper through the design of the induction quenching sensor and the quenching process has been studied and verified by actual production, and good results have been achieved.