The ride comfort and handling stability of vehicle are affected by nonlinear characteristics of active suspension system directly. The dynamic model of 1/4 vehicle body nonlinear active suspension system was established by considering the nonlinear factors of spring, damper and tire, and the system was transformed into an affine nonlinear system. The nonlinear dynamics model was linearized based on differential geometry theory, and the control law of the actuator for the active suspension system was obtained, then the optimal control method was used to obtain the system’〖KG-*2〗s optimal feedback gain. The influences of nonlinear factors on the suspension system and the control effect of the optimal controller based on the differential geometry theory on the nonlinear active suspension system were studied by MATLAB simulation. The results show that the nonlinear parameter c2, ε and ktt lead to serious bifurcation, which reduce the stability of the system; the designed controller can effectively improve the response characteristics of the active suspension system, and reduce the adverse effects of nonlinear factors on the system. The research conclusion can provide some theoretical reference for the research of nonlinear active suspension system.