Abstract: This paper analyzes the ditch-crossing gaits of a quadruped walking vehicle in its straight movement. First ofall, the kinematic characteristics of perodic gaits of the walking machine before it crosses ditches have been des-cribed by using the concept of phases. Based on this description, several problems, including the determination ofmaximum ditch-crossing ability of the walking machine, thc selection of initial preditch-crossing position, theplanning and optimizaion of posture adjusting gaits and the determination of stability etc., have been analyzed andstudied, and the possible solutions to these problems have been proposed. Finally, a set of simple and practical follow-up ditch-crossing gaits has been presented from the point of view of simplicity and versatility, providing use-ful information for the realization of ditch-crossing for quadruped walking vehicle.