One of the important factors affecting the performances of semi-active suspension control is how to obtain the terrain information. A preliminary study is conducted to detect and memory the road conditions by which semi-active suspension switches control strategies or certain damping from one to another. The suspension adopts skyhook controllers designed for halfvehicle model in random road and uses small damping while passing an obstacle. The navigator advance informs the suspension controller as soon as it detects obstacles in front. Then the controller switches to small damping,thereby reducing the peak vibration and improve driving ride. Simulation proves the validity of this idea. Experiment using a real car is conducted after an onboard navigation system developed and the road conditions detection and memory search strategies are available. The experiment and simulation achieve similar results.