Most structures of vehicle are composed of many substructures connected to one another by various types of mechanical joints. In vehicle engineering, it is important to study these jointed structures under random frequency vibration for the evaluations of fatigue life and stress concentration exactly. It is rarely obtained the accurate load history of specified positions in a jointed structure because of the errors such as modeling, measurement, and etc. In the beginning of design, exact load data are actually necessary for the fatigue strength and life analysis to minimize the cost and time of designing. In this paper, the hybrid method of practical dynamic load determination is developed by the combination of the principal stresses from F. E. Analysis and test of a jointed structure. Least square pseudo inverse matrix is adopted to obtain an inverse matrix of analyzed stresses matrix. The error minimization method utilizes the inaccurate measured error and the shifting error that the whole data is stiffed over real data. The least square criterion is adopted to avoid these errors. Finally, to verify the proposed system, a heavy-duty bus is analyzed. This measurement and prediction technology can be extended to the different jointed structures.