Road detection is a sub-system of vehicle intelligent auxiliary drive system, which includes such sub-projects as road segmentation and road recognition. The image from CCD camera is processed, and road line is abstracted from it through image process. Then the direction of the road, such as left or right, can be identified according to the road line. Because of the special requirement, i.e. the rigid real-time requirement, the algorithm adopted must have the very low time cost. Through many experiments, a kind of recognition algorithm is proposed based on region-growing process and curve fitting, which was verified to have good effect.