At present, with the quick development of auto industry, the requirements for the precision of auto change gear were constantly raised, and meanwhile the corresponding manufacture process and tooling keeps innovating as well. This paper introduced an innovative improvement for the spring sleeve of expanding mandrel fixture and the working cone angle of rigid shaft by taking advantage of the property that the expanding mandrel has small clamping process, which results in the elastic clamping force jamming the inner hole of workpiece tend to be equivalence along the inner hole shaft when this particular fixture is used to position the workpiece. Confirmed by the production practice, the centering precision has been greatly improved by using this particular fixture to position the workpiece. The high precision of gear grinding could be guaranteed, and the clamping of the workpiece will become faster and more convenience. Therefore, the production efficiency will be improved and it will benefit the realization of the workpiece clamping automation.