Abstract: The 9-linkage model of biped robot with heterogeneous legs is given. After building a constraint equation of this robot machine including closed-chain, using multi-body dynamic Lagrangian equation to establish the dynamic equations of this robot system. Determines the differential coefficient of constraint equation to get extended differential equations, then adds them to the system's dynamic equations which are higher-order differential-algebraic mixed equations so as to use numerical integration algorithm. Error feedback control is designed to decrease computing error and insure the convergence of this algorithm. Algorithm simulation computing is done to solve the dynamic equation of the bionic leg. Errors of numerical integration with and without error feed back control are compared. All results show the modeling is right and the error feedback control method can improve the precision of numerical integration algorithm and avoid the errors to be cumulated.