IN THIS STUDY, A DYNAMIC GAIT OF A QUADRUPED WALKING ROBOT IS NUMERICALLY INVESTIGATED WITH A THREE-DIMENSIONAL DYNAMIC MODEL. A GAIT PATTERN NAMED SIMPLE TROT IS ADOPTED FOR THE SIMULATION. SEVERAL CONDITIONS FOR THE GAIT PATTERN ARE ASSUMED TO SIMPLIFY THE WALKING STRATEGY. ALSO, THREE GAIT FEASIBILITY CONDITIONS ARE ESTABLISHED. FROM THE DYNAMIC SIMULATION, IT IS FOUND THAT THE BODY SHAKING DURING THE WALKING CYCLE IS REDUCED AS THE WALKING SPEED INCREASES. FOR A GIVEN WALKING VELOCITY, THE LARGER VALUES OF THE GAIT PARAMETERS, SUCH AS DUTY FACTOR AND THE PHASE DIFFERENCE, PROVIDE THE MORE BODY BALANCE WITH THE LESSER BODY SHAKING. ALSO, THE BODY HEIGHT AND PITCH SHOULD BE LARGE COMPARING WITH BODY WIDTH TO MAINTAIN BODY BALANCE AND TO REDUCE THE BODY SHAKING. THE PARAMETERS OF DYNAMIC GAIT ARE CHECKED FOR SATISFYING THE FEASIBILITY CONDITIONS THROUGH THE NUMERICAL SIMULATION.