Abstract: A hydraulic bilateral rolling shear is the composite connecting rod shearing mechanism with the upper blade driven by servo-cylinders. Because an interaction between the mechanical dynamics and hydraulic dynamics of the machine and the hydro-mechanical interaction has a positive feedback component, which produces instability phenomenon. In this model, all instabilities energy comes from the fuel. A hydraulic servo system model was established based on unsymmetrical valve controlling unsymmetrical cylinder and the nonlinear equation of the state between force and cylinder flow was proposed. Moreover, Lyapunov stability theory was used to analyze the stability of system. Based on field experiment data, actual trajectory agrees well with given trajectory, showing that this method can meet the practical demand in engineering.