In this paper,firstly,the conditions for two output shafts with opposite but uniform speed are analyzed.Secondly,a bond graph model of coaxial dual-output reducer is established on the basis of bond graph theory,in which such factors as average mesh stiffness,rotational inertia and damping are considered.Then,according to the causality and power flow in bond graph,the corresponding equation of state is derived,and a system simulation is conducted to discover the variations of system variables with time and to explore the transmission performance and dynamic characteristics of the system.Moreover,the influences of various parameters on system's dynamic charac- teristics are analyzed by comparing the response curves of output shaft speed at different parameters.Finally,a sim- plified model of coaxial dual-output reducer is established,a virtual prototype experiment is made,and the results are compared with those obtained by bond graph method.It is found that the bond graph theory is effective in the dynamic simulation of coaxial dual-output reducer.