Abstract: Using Newton-Euller method, a dynamics model of biped robot with 12 degrees of freedom was built, and then a sliding-mode control model of biped robot was also built. Stability analysis of sliding-mode control is made by a simpler Lyapunov function, and the angle acceleration of 12 degrees of freedom is compensated using the sliding-mode control method. To prove the effectiveness of sliding mode control method on trajectory tracking control, a simulation experiment was done, where the random errors of some given ranges were added to every joint angle instead of the errors caused by such factors as the structure parameters, moment of inertia and friction. The experiment results show that the trajectory tracking errors of angle and angle velocity at each joint angle are small insomuch that the expected effect comes true and prove that the sliding-mode control method Is available to control the trajectory tracking of biped robot with 12 degrees of freedom.