Effect of laminar flow extent on drag reduction characteristic based on engineering practice is developed for some civil plane, which can be the important means to improve the economy. It is simulated for the wing-body model at Reynolds numbers 10 million and 18 million, with the laminar flow extent be kept respectively 7%, 15%, 20%, 30%, 40% of the local chord of wing. The frictional drag coefficient is effectively decreased as the laminar flow extent is increased. Compared with the full turbulence state, the drag can be reduced by about 11 percent and the lift-drag ratio can be increased by 12.3 percent when the laminar flow extent is kept with 40 percent, and drag reduction benefit can be obtained more at lower Reynolds number.