Abstract: The analytical solution for analyzing motion responses of the two dimensional planning boat in the uniform flow is presented by the CFD software.The results of the fluid dynamics are used to derive the motion responses of the planning boat.Numerical simulations of the pitch and heave coupled motion were performed under four different Froude numbers.The characteristics of magnitude of the heave and trim angle varying with the time,as well as the law of resistance,lift and moment changeing with the Froude numbers were derived.In addition,the period of the stable state when the planning boat can be reached and the dynamic pressure at the bottom of the planning boat when in sliding condition were also analyzed.Results show that the time needed for reaching the stable state need only 80 seconds under Froude number 1.5,and the planning boat will tend to be in a ＂＂dynamic-balance＂ state except for the serious oscillation under Froude number 2.0.