The self-floating elevating navigation mark platform is a new type of water navigation mark platform device，and it can adapt to large water level changes through the sliding of the floating body on the guide column. The draft of the floating body platform is an important factor affecting the stability of the floating body. The relationship between the draft of the floating body and the center of mass and the center of buoyancy is derived by formulas.Through the hydraulic physical model test，the law of the stability change of the floating body caused by the changes of the draft is observed and analyzed，and the movement of the floating body is simulated by the finite element software. Finally，the response law between the draught of the navigation mark platform and the stability of the floating body is obtained.