The optimization of 2D expansion lines and key parameters of three-dimensional configurations was carried out under simulated conditions of Mach 6.5 and a flight altitude of 25 km for an integrated configuration of the afterbody/nozzle of a hypersonic vehicle.First,the cubic B-spline method was applied to parameterize the expansion lines of the upper expansion ramp.The optimization procedure was established based on computational fluid dynamics and the sequential quadratic programming method.The local mesh reconstruction technique was applied to improve computational efficiency.A three-dimensional integrated configuration afterbody/nozzle was designed based on the two-dimensional optimized expansion lines.The influence rules incorporated certain key design parameters affecting the lift and thrust performance of the configuration,such as the ratio of the lengths of the lower expansion ramp to the afterbody (l/L),the dip angle of the lower expansion ramp ω,and the ratio of exit height to the length of afterbody (H/L).Under these conditions,we found that the integrated configuration has optimal performance when l/L=1/6,H/L=0.35 and =10°.We also showed that the presence of a side-board promotes lift and thrust performance,and effectively prevents the leakage of high pressure gas. The optimization of 2D expansion lines and key parameters of three-dimensional configurations was carried out under simulated conditions of Mach 6.5 and a flight altitude of 25 km for an integrated configuration of the afterbody / nozzle of a hypersonic vehicle. First, the cubic B- spline method was applied to parameterize the expansion lines of the upper expansion ramp. The optimization procedure was established based on computational fluid dynamics and the sequential quadratic programming method. The local mesh reconstruction technique was applied to improve computational efficiency. A. three-dimensional integrated configuration afterbody / nozzle was designed based on the two-dimensional optimized expansion lines. The influence rules incorporated certain key design parameters affecting the lift and thrust performance of the configuration, such as the ratio of the lengths of the lower expansion ramp to the afterbody (l / L), the dip angle of the lower expansion ramp ω, and the ratio of exit height t o the length of afterbody (H / L) .Under these conditions, we found that the integrated configuration has optimal performance when l / L = 1/6, H / L = 0.35 and = 10 ° .We also showed that the presence of a side-board promotes lift and thrust performance, and effectively prevents the leakage of high pressure gas.