Based on the requirement of CF700 tractor front axle suspension parameter, a hydropneumatic suspension with controllable stiffness and damping was designed. The stiffness and damping mathematical model of hydropneumatic suspension was established and the structural parameters were calculated. Characteristics of the dynamic stiffness, damping force and output force under various work conditions of hydropneumatic suspension and the influences of the structural parameters on suspension output force were simulated. The results show that when rod cavity and rodless cavity of hydropneumatic spring cylinder connects, the damping force and suspension output force are smaller than two separated oil cavities. By adjusting the throttling area when two oil cavities connect can adjust the suspension damping force and output force. By additional connecting an accumulator, the dynamic stiffness and output force of the hydropneumaticspring are significantly reduced. The throttle aperture size of proportional valve affects the suspension damping force and output force, the greater the throttle aperture, the smaller the suspension damping force and the output force. The designed hydropneumatic spring can realize the “soft” and “hard” state switch of suspension stiffness and damping, and the stiffness and damping are available to be controlled at a certain range. Bringing the linearization of stiffness and damping coefficients of front axle suspensions to the vibration simulation model,it is shown that the RMS of seat position vertical vibration acceleration, the RMS of seat position pitch angle vibration acceleration and the front tire dynamic load of tractor with front axle suspension are respectively reduced by 92%、424% and 703%. The tractor driving safety and ride comfort are improved. The study provides important basis for the later development of the semiactive hydropneumatic suspension.