This paper suggests how to improve fatigue strength of the drive shaft, which is the vulnerable part of the drive shaft system for the 3.5ton commercial vehicle. Drive shaft is composed of the university joint with spider and yoke, yoke shaft and so on. Improvement of drive were selected shaft inner/ outer yoke shaft spider. Four cases were considering design variables such as length and thickness of spider of drive shaft, fatigue analysis was conducted. Finally, we suggest that be improved drive shaft.