An Over Head Transportation (OHT) vehicle is used to transport large loads in a factory more efficiently. To maximize productivity, the speed and load requirement for the OHT vehicle is continually increasing. This may create a repetitive dynamic load and thus cause fatigue failure in related components. In this paper, a computer aided engineering (CAE) method is proposed for fatigue life prediction in the early design stage using multibody dynamic analysis and the linear damage rule. The process of predicting the fatigue life using the proposed computer models in this paper may be applied to structures of various mechanical systems.