Abstract: For a sixlegged vehicle with 18 degrees of freedom, among its three groups of values, I. E. the position and posture of vehicle body, the angles of every joint in legs and the positions of every foot tip, there are definite relations. In this paper we reveal the relations and get the method to calculate a group of values when we know the other two. Using above results, we also simulate the walking process of sixlegged vehicle on irregular terrain and draw out its solid graph at any moment by means of a computer.