Mechanical fatigue subjected to external and inertia transient loads in the service life of truck cab often leads to a structural failure due to accumulated damage. Structural durability analysis that predicts the fatigue life of mechanical components subjected to dynamic stress and strains is a computer intensive multi-disciplinary simulation process, since it requires an integration of several computer aided engineering tools and large amount of data communication and computation. In this paper, a detailed method for fatigue life estimation of the truck cab with spot welds by using finite element analysis is presented. The stresses in the cab are obtained by using static analysis with inertia relief. The load history is estimated by using the multi body simulation. With these values damage from the stress time history is estimated and thus finally calculating the fatigue life of a truck cab. The accuracy of the proposed method is shown by comparing the numerical results with the experimental results.