This paper addresses the effect of ankle joint position on the walking behavior of a biped robot. The mentioned foot structure consists of a tiptoe and a big toe inspired by the human foot which have a crucial role on moving stability. The study subject is a small robot called Kondo KHR-3HV, belonging to the Kondo Kagaku Company. Due to the small size of the robot and considering a reduction in energy consumption in toe mechanism, a passive joint using torsion spring was selected as a toe joint. The gait generation method, for finding the proper position of ankle joint, is used by varying the ankle joint position. There are two requirements of robot design: go straight and stay within setting conditions. The paper is implemented by two stages. First, the biped robot locomotion is considered by different stiffness coefficients to find out what is the proper stiffness coefficient. In the second stage, the simulation of all small biped robot models which have the different ankle joint position, can walk within setting conditions, is implemented. The results are compared to the human ankle joint trajectory in gait performance and frequency and are confirmed by dynamic simulation on Adams (MSC company, USA).