The linear vibration isolator on the traditional seat suspension has poor low-frequency vibration isolation capability and is difficult to cope with wide-frequency excitation. This problem can be solved by designing a nonlinear vibration isolator. In this academic paper, a seat suspension possessing a non-linear stiffness configuration is engineered, and an active controller is developed specifically for this suspension. The nonlinear characteristics of the seat suspension with high static and low dynamic stiffness are obtained by using a cam surface and a scissor structure. This structure significantly reduces the resonant frequency of the suspension. Then, a sliding mode controller is designed to achieve active control of the seat suspension. Finally, simulations under various excitations are conducted to evaluate the vibration attenuation capabilities of passive and active seat suspension, both those with and without nonlinear stiffness. The simulations show that the RMS value of the acceleration of the nonlinear stiffness suspension decreases by 62.7% and 59.2% under the conditions of sinusoidal excitation and random excitation, separately. The active controller can significantly improve the vibration reduction effect further.