Abstract: Aim To give a new method of analyzing stability of time-varying and nonlinear control systems. Methods Considering the inputs of control systems as the time-varying parameters of the control systems, the influence of the control system input on system stability was studied . Results Some examples were given to illustrate the effectiveness of this method.Conclusion Combined with the method of equilibrium control theory, a new train of thought and method for stability analysis of time - varying and nonlinear systems is given.