In order to study the mechanical features of the equilibrator of coordinator in the further, the influences on performance of the machine caused by the stability of piston rod and the position of equilibrator are studied. Based on multi-body system dynamics and virtual prototype technology, virtual prototype model is established by means of ADAMS software. Taking advantage of the model, force analysis and check of instability are performed on piston rod of equilibrator and the influence on torque of coordinator caused by change of equilibrator’s position is studied. The simulation results indicate that the method determines the relation between the change of position and the max torque and results supply data basis for the stability study on equilibrator.