Abstract: Young equation is concluded according to the mechanical equilibrium of the physical model.The article concludes the relation between surface tension and wetting angle by the principle of energy,as a result,both the conclusion concluded and the Young equation are unanimous.Wetting angle is an important factor to evaluate wetting ability of filler material.However,it is difficult to obtain the value of surface tension of materials and then solve the value of wetting angle by Young equation.If we measure wetting angle by instrument,the experimental cost will rise and experimental efficiency will decline.In this study,we establish a simple mathematical model of calculating wetting angle and compare the calculated results with the measured results,and the result shows that the distinction of them is little.