The purpose of this research is to optimize on an optimal condition to increase the capacity of FSR ISUZU passenger truck chassis and focus analysis of stress for the different crosssection in different loading condition with the consideration of stress concentration factor. Chassis is a major component in the vehicle and different type of failures is occurring due to static loading condition. Unbalanced loading condition in the construction of FSR lorry and FSR passenger truck, the actual unloading carrying capacity for passenger bus is less compared to the lorry one in the local area. Maximum stress and maximum deflection are the main criteria for the design of the passenger truck chassis and the present study determined the maximum stress and maximum deflection to recognize critical regions under loading. Stress analyzed using different cross-section under different loading condition with the consideration of stress concentration factor. As the result shows that I cross-section is important to increase the capacity of the chassis and the effects of stress concentration factor are necessary to choose the essential profile. And that used to fix chassis characteristics of the static condition. Finite element analysis enables to predict the region that tends to fail due to loading implemented in this study besides classical theoretical analysis. This study definitively answers the question regarding FSR chassis stress analysis in different crosssection and loading condition. And so, I cross-section is the best which has less stress and deflection.