Abstract: In view of that traditional spoiler can only reduce aerodynamic drag or lift force, a novel spoiler, which can reduce both drag and lift force, is designed based on a square-back vehicle. Firstly, according to the flow field condition the spoiler should meet, the initial upper and bottom curves of the cross-section of spoiler are determined and fitted by quasi-uniform B-spline curve,and are drawn along y direction to form the surface of spoiler. Then a series of surfaces are obtained by changing the control points of section curves, among which an optimum surface is obtained by using genetic algorithm. Finally, for further reducing the drag and lift force, a further optimization is conducted by adopting the design of experiment, approximate model and NSGA-II genetic algorithm and changing the width and the installation position and angle of spoiler based on optimum surface of spoiler. The results of verification experiment on model wind-tunnel show that with the spoiler optimized the drag and lift force of vehicle reduce by 3.8% and 7.9% respectively

Key words: novel spoiler, drag and lift reduction, wind tunnel experiment