Abstract: A special research was done on the dynamic modeling of a biped robot with heterogeneous legs of which one is a bionic leg and the other is an intelligent prosthesis. To make the robot walk with an expected gait, a special multi-pivot mechanism with closed chain was designed and used at the knee joint of the intelligent prosthesis, but it brought a difficulty to the dynamic modeling if comparing it with the single-pivot mechanism. For the characteristics of closed chain with redundant coordinates, the Routh equation was applied to developing a dynamic model of the biped robot with heterogeneous legs to which the relationship between force and moment of the two legs are evaluated, thus giving dynamically the direct and inverse solutions to the Routh equation. A simulation was also carried out to calculate the equation of dynamic model with typical gait data. The result showed that the reluctant constraint equation can therefore be avoided. What the research concluded provides a foundation to investigate further the locomotion, control and perception of the robot.