In this work, a new model of active suspension on a half-car with a wheelbase preview of information and a nonlinear differentiator are developed. First, a sensor placed on the front suspension collects and sends road input as preview information to the rear suspension system. Then, with given preview information and the feedback signal of vehicle state, an enhanced Proportional-Integral-Differential (PID) controller combined with a nonlinear differentiator is used to generate control signal to apply active force on rear suspension in order to attenuate the suspension vibration. The PID controller with a nonlinear differentiator provides more stable results than regular PID control in the presence of noise. The numerical result further shows that with preview information considered, the accelerations of the unsprung masses in the front and rear wheels both decrease in comparison to those of the suspension controlled by regular PID control. The active suspension system developed in this work is then tuned by using Genetic Algorithm (GA) to obtain optimum configurations on several design parameters so as to achieve a better ride quality.