Abstract: A valuable computation model based on Greeng theorem is constructed to tackle the wingin-ground effect problem. In this model, Rankine Sources and dipoles are placed on boundary surfaces, the steady method is used to compute the performance of 2D wing-in-ground (WIG) effect. Theory development and computation process of this method are discussed in details, and proper parameters of the model are determined by many numerical tests. The influences on the lift of 2D WIG effect are discussed by means of the adjustment of various parameters, such as the ground clearance, angle of attack. The comparison between various numerical results and real experimental data show that the method is a feasible and reliable supporting model of WIG effect problem.