Most of the component optimizations of trucks are limited to the individual component because of the complex coupling relations between components. Focusing on such difficult optimal problem, the conception of static modal stiffness was introduced and static modal stiffness sensitivity was defined. The method for computing static modal stiffness sensitivities was also developed. The proposed method was applied to the static modal stiffness sensitivities analysis of the frame of the truck under full vehicle environment. In the computations, a three dimension finite element model for full vehicle was established and the frame was divided into 13 superelements. The static modal stiffness sensitivities obtained can be used to improve the frame design.