Abstract: Bolt, as one of the important links in car assembly components, the reliability of its connection, will be directly related to the safety of the vehicle. In this paper, through force analysis in the process of screw, combined with the actual loading test, gives the set screws （without self-tapping screw） torque method, and compiled a set of small procedures, conducive to engineering practice, a more accurate and effective control of bolt pre-tightening force.