Abstract: Trajectory tracking on the ground is an elementary technique in vision guided robot systems.In this paper a novel state based control approach is proposed for tracking trajectory whose curvature changes greatly.Input of the state based tracking control is achieved by extracting reference trajectory direction and amplitude parameters from vision images,and the tracking control is realized by regulating translational and rotational velocity for output.In order to improve the control performance,when the image distortion is too large resulting from camera obliquity,these parameters are transformed from image coordinate to robot coordinate through projective transformation,while parameters such as position and curvature are not necessarily provided.Experimental results demonstrate the validity of the approach.