Walking machines may not be more common or faster than the transportations with wheels. It can¡¦t be ignored in the occasions of unknown terrain. This paper is going to discuss about how a walking machine get faster and be static stable. When the quadrupeds walk toward, the wide won¡¦t be changed. So that, longitudinal stability margin can take the place of stability margin to simplify gait problems. Meanwhile we can get the optimal gait. In the past researches, there is only one kind of walking type will be discussed in one time. This is because there are not so many relationships between different kinds of movement. If we take one step ahead to discuss the optimal gait, it will be more difficult. If there was a way to get into optimal gait from random initial position, we can connect one movement with the other. The velocity was constrained while the quadruped modal has had been made since 1968 by McGhee. We will try to change the working area to approve the performance. As to the researches of multi-legs walking machine, most of them talk about quadrupeds and hexapods. it will be less if the more legs we are talked about. To maintain stable tread, a walking machine request four legs at least. We can regard a quadruped as a unit, and divide a multi-leg working machine in to many quadrupeds. By using the method of quadruped analysis, we can simplify multi-legs gait algorithm problems.