By taking a large WIG craft as the research object, the numerical simulation of aerodynamic characteristics of the cruise state of WIG craft was calculated based on the finite volume method for solving Navier-Stokes equations. The trend of the lift-drag characteristics of WIG craft with the wing incidence angle and the relative flight height was obtained. The best wing incidence angle was selected as 5.5° by the comprehensive consideration between the lift-drag ratio and drag. The best relative flight height was selected as 0.5 by the comprehensive consideration between the lift-drag ratio and the safety and maneuverability of cruise state. By taking a large WIG craft piggybacking a load aircraft as the research object, the numerical simulation of aerodynamic characteristics of the piggyback cruise state was calculated. The trend of the lift-drag characteristics of the piggyback cruise state with the angle of attack of load aircraft was obtained. The best angle of attack of load aircraft of the piggyback cruise state was selected as 3° by the comprehensive consideration between the economy of the piggyback cruise state and the safety and reliability of the transition from cruise state to separation state.