This paper presents a control method of the torso for dynamic walking of biped robots. Specifically, we want to save the energy and improve the walking stability by the planning and control of torso orientation at landing. First, the impact process of leg exchange is formulated using a simplified model. Based on this, the influence of the torso orientation at landing on walking performance is investigated. Second, a control method of torso orientation, which is an under actuated control, is proposed to regulate the torso orientation in the single support phase (SSP). Third, the control module of the torso is integrated into the previously established control frame of 3D biped walking to implement the control objective of a 3D humanoid robot. The results of a number of simulations show the feasibility of the proposed method, and also explore the relations between the speed, stability and energy consumption with the landing orientation of the torso.