Real-time gait generation algorithm for humanoid robot is presented in this paper. The 3D foot motion planning for the humanoid global motion is developed in order to walk in any surface as plane, ramp, climbing stairs. Furthermore, it is possible continuous change the step length and orientation in real time.. The proposed algorithm takes into account physical robot constraints as joint angles, angular velocity and torques. Torques are computed by Lagrange method under Lie groups. Some results are shown and discussed.