Abstract: In order to calculate the lifts of rectangular wings with different winglets at subsonic speeds, we have adopted the finite element method which divides spanwise lattice and determines spanwise locations of control points by means of a constant roll-angle method. The induced drags are also calculated by using combined flow field method.As the results of calculating various configuration of a winglet, we have found out some rules affecting the lift and drag characteristics of wings with winglets and picked out a favourable configuration from them. The aerodynamic mechanism of winglets is also discussed.