The moment generated by torsion of straight bars with multiple sub-rectangles plays an important role in practical engineering, especially in an armored vehicle. With the increment of time or load application times, the strength of straight bars will be degraded, which will impact the moment generated by the torsion of straight bars. With the strength degradation of straight bars, the failure reliability will increase. So, in this paper, we will study the reliability analysis of straight bars with multiple sub-rectangles. First, we will study the moment generated by the torsion of straight bars and get the relationship between the moment and the numbers of straight bars. Then, the strength degradation of moment will be studied. The stationary stochastic process will be chosen to describe the moment degradation caused by the strength degradation of straight bars. Finally, the reliability based on strength degradation will be got. The results can give us a guide to choose the suitable number of straight bars to generate sufficient moment need by practical engineering. And after studying the relationship between reliability and strength degradation, we will know when or how many times of load application to change the straight bars with multiple sub-rectangles to guarantee the normal operation of practical engineering.