Modern and reliable tightening spindle systems are indispensable due to importance of bolt connection in assembly technology, and the tightening spindle system is developed in order that automated tightening processes is able to ensure uniform quality of the tightened bolt connection. In this paper, the strategy “torque control and angle checked” of tightening is discussed and analyzed on the basis that the process mechanism of forming bolt connection is clarified. This strategy builds the base and boundary conditions of modular design strategy for tightening spindle system which is introduced, because it makes design flexibly, and many standard components can be chosen with more efficiency and low cost. The module partition bases on the function of the components of the system. The possibility of expansion of the tightening system comes into discussion too.