Abstract: The relation among the bevel drive pinion bearing preloads, axial displacement and locknut screwing moment and the relation between the frictional moments were analyzed in this article. Based on the analysis, the control system??of the equipment of automatic assembling bevel drive pinion was developed,which had the function of automatic measuring screwing moment and start-up friction moment. Having industrial PC as control centre and using the software Visual C++ as developmental tool, the control system can have control over the bearing preloads accurately by means of closed-loop real-time measuring screwing moment and start-up friction moment, and the assembling quality and efficiency of bevel drive pinion assembly are improved accordingly?.