Abstract: To aim at analyzing the variation of the aerodynamic performance as well as the volume of hypersonic vehicles caused by the modification of the upper surface, a two-dimensional multi-objective optimization study is carried out by considering the design condition of flight Mach number 6.5, flight altitude 27 km, and 4? flight angle of attack. The CFD-embedded pareto genetic algorithm is used as the optimization driver. On the basis of 2D optimization results, several typical 3D configurations are generated, and a primary relationship between the aerodynamic performance and the volume is obtained by numerical simulation. The results show that the lift-to-drag ratio is approximately linear inverse proportion to the volume for both two-dimensional and three-dimensional configurations, though there are significant di erences between the 2D and 3D aerodynamic coe cient values. Moreover, the lift-to-drag ratio can only gain a little increment (about 0.36%) by adjusting the symmetrical profile shape of the upper surface when the volume is a constant, while the volume has a relatively large adjustable range (about 1.93%) under the condition of fixing the lift-to-drag ratio. Besides, the numerical results also demonstrate that the adjustment range of the pitch moment of the vehicle is about 5% by modifying the shape of the upper surface when the lift-to-drag ratio and the volume are all fixed simultaneously.