Abstract: In order to solve the stable control problems produced by the nonlinear planing force between supercavitating vehicle and supercavity,a circle-criterion-based stability analysis method and its optimal control law are proposed.With the supercavitating vehicle model proposed by Dzielski as the research object,a series of system transformations are performed,and the supercavitating vehicle model is transformed into the feedback connection between a linear part and a nonlinear part.The sufficient condition of global system stability is obtained based on circle criterion by mapping the Nyquist plot of the system,which simply solves the problem of stability criterion in Dzielski's model.In order to solve the problem of system instability caused by actuator saturation,an optimal control law is designed,which achieves stability control of the supercavitating vehicle system when the control variables are restricted.Simulations are made to validate the effectiveness of the proposed method.