To investigate the influence of the structure of legs on walking gait patterns of bipedal inverted pendulum, a bipedal model with two-segment legs was proposed. The relationship between the reaction force on the leg and the length of the leg was determined. Functions of motion and the simulation model of the proposed bipedal model were built. Periodic walking gait patterns were solved with Poincare return map and Newton-Raphson algorithm. Influences of model parameters including mechanical energy, attack angle, knee rest angle, and joint stiffness on gait patterns were analyzed. Analytical results show that the initial stiffness of the two-segment leg was large, while it gradually decreased with the increase of the deformation of the leg, indicating that the two-segment leg may soften with deformation. The proposed bipedal model could achieve various walking gait patterns in a certain range of parameters. It could also cover the range of the pacing rate of normal human walking, if the values of the parameters were well selected. Compared with models with linear spring legs, the proposed model was closer to the body structure of real human, and the physical meanings of its parameters were clearer, which lays foundation for experimental verification and parameters calibration of the model.