Abstract: This work deals with the stability analysis of two legged (humanoid) robots during walking. This research area is characterized by the fact that there are a lots of publications, a method for synthesizing the gait of a planar biped walking on level ground is presented. Both the single support phase (SSP) and the double support phase (DSP) are considered. A complete step can be divided into a SSP and a DSP. The SSP is characterized by one limb (the swing limb) moving in the forward direction while another limb (the stance limb) is pivoted on the ground. This phase begins with the swing limb tip leaving the ground and terminates with the swing limb touching the ground. Its time period is denoted as TS. In the DSP, both lower limbs are in contact with the ground while the upper body can move forward slightly. The time period of this phase is denoted as TD. In the following step, the roles of the swing limb and the stance limb are exchanged. It has been noticed that the joint angle profiles can be determined if compatible trajectories for the hip and the tip of the swing limb can be prescribed. Also is presented in practical implementation in a real robot.