The lift loss flow field calculation model of short/vertical takeoff and landing (S/VTOL) aircraft proximity of the ground was built. The two order response surface function of lift loss about nozzle pressure ratio(NPR)

velocity of the cross wind and height of the plane above ground

as well as the key factors affecting the lift loss significantly at multi working states proximity of the ground were obtained by response surface method. The interaction effect of NPR

velocity of the cross wind and height of the plane above ground on the lift loss was analyzed and the minimum lift loss in certain range of working state was optimized. The study shows that the lift loss reduces with the increasing height of the plane above ground and NPR and increases with the velocity of the cross wind when considering single factor; the interaction effect on the lift loss exists between height of the plane above ground and NPR

velocity of the cross wind and NPR

the interaction effect on the lift loss doesnt exist between height of the plane above ground and velocity of the cross wind

the minimum lift loss obtained by optimization is at height of the plane above ground of 9D (D is nozzle diameter)

nozzle pressure ratio of 3

velocity of the cross wind of 0m/s working state

and the corresponding lift loss is 1.3%.