Based on the test results of tunable damper, the nonlinear relation was fitted between the damping and the angle of the stepping motor. The mathematical model of semi-active suspension with nonlinear damping was built and fuzzy dynamic optimal control strategy was designed. The controller of semi-active suspension with nonlinear damping was developed. On the basis of the simulation, the actual road test has been done. The results showed that the model of semi-active suspension with nonlinear damping was closer to the actual model, the comfort and the security were effectively improved and vehicle performance was coordinated.