Biped passive dynamic walking is a promising idea towards the goal of humanoid robotics further after the proposal of the upper body in these years. In this paper, we deduce the dynamic robot model with the upper body based on bisecting hip, in which the section of the swing phase is performed by Lagrange method, while the section of the collision phase is completed in terms of the principle of angular momentum conservation. The analysis of the global stability and the local stability are combined with each other, based on which the configurations of parameters with different mass and size of the upper body are discussed. Finally the optimized configuration of the model is obtained after the simulation in Adams environment. Results verify that the model with an upper body exhibits an extraordinary stability and robustness under circumstances of either a single disturbance or random disturbances.