Natural dynamics can be exploited in the control of biped walking robots: the swing leg can swing passively, the compliant ankle can naturally transfer the center of pressure along the foot and help in toe off.These mechanisms simplify control and result in motion that is smooth and natural looking.Imitated human beings behavior, we presented a control strategy for HIT-III biped robot, in which active and passive motions were combined.The experiment result shows that robot walked at a faster speed (approximately 0.25m/s) than previous and had a natural and smooth looking gait.