Abstract: A simulation model of a biped robot with torso was established using Matlab, the passive dynamic walking of this model was studied, the stability of the walking was analyzed, and a full-state linear feedback walking stabilizer was designed. Simulation results show that the model can walk down a slope without any actuator and there are two unstable walking gaits on the same slope. The results also indicate that the model can realize stable walking by adopting the full-state feedback stabilizer.