Conventional leaf spring suspension in heavy duty trucks can afford large carry capacity and better handling stability ability but less ride performance. In this paper a semi-active control was embed to the leaf spring suspension. The dynamics model of semi-active leaf spring suspension was built and analyzed. A full function heavy duty tractor using virtual prototyping was built and assembled in dynamics simulation software. A bumpy road test was performed to verify the performance of the proposed semi-active suspension. The results show that the semi-active leaf spring suspension proposed in this paper can improve the ride performance of the heavy duty trucks. The occupants in the vehicle cab will feel more comfortable.