Abstract: Study on the gaits of legged locomotion systems is indispensable to geometric designof real machines.In this paper,the authors study the gait selection problem of six-legged laterally-walking robots,employing both longitudinal and general stability ma-rgins as criteria of evaluating the static stability of a legged locomotion system.After optimization calculation on a computer,it is shown that there exist a groupof optimal gaits which are defined by the authors as quasi-tripod gaits.In the secondpart of the paper.the authors analyse such kinematic characteristics as staticstability,slope negotiation capability,and ditch negotiation capability for quasitripodgaits.Relationship between these characteristics and several geometric parameters ofthe robot is established.