The study of biped robot has long history and continuation. One of important moving processes is walking procedure. The walking posture is an important research field that always adapts and implements in the biped robot. The walking research field is very interesting because the walking posture of humans is flexible and stable. Additionally, the force that affect on the humans foot is also investigated. This research addresses the walking simulation of small biped robots that have tiptoe and bigtoe. The study based on the assumption that the bigtoe size affects on the walking posture and walking distance. The gait generation method, for finding the proper size of bigtoe, is utilized by varying the bigtoe size. There are two requirements of robot design: go straight and stay within setting conditions. The simulation results of all small biped robot models which have the different bigtoe sizes can walk within setting conditions. There is only one model its bigtoe width per foot width ratio equals 0.28 (or 28% of foot width) has the longest walking distance. Moreover, this ratio is equal to the ratio of humans foot.