A six-legged parallel suspension system for tractor cab vibration reduction was designed. Aimed to the problems to determine the physical and geometrical parameters of the tractor cab hexapod parallel suspension system, the 6-DOF dynamic model was established based on the Lagrange Equation. Taken the natural frequency of the suspension system, and the damping and decoupling degrees of cab in six direction as optimize target, multi-objective optimization model was established and the sensitivity method was used in the system optimal design research. Compared with the traditional rubber liner suspension system of tractor cab, the results proved that it had good damping effect, and provided a theoretical basis for parameter selection for passive vibration control and the manufacturing of suspension system prototype.