Hull shape optimization is one of the effective methods for drag reduction of stratospheric airship. Transition, especially crossflow transition, has a great influence on the drag characteristics of threedimensional hull. SST-k-ω turbulence model coupled with γ-Reθ-CF transition model considering crossflow effect was used to calculate the flow around the hull, the calculation was running on the highprecision CFD software platform. Firstly, the numerical method was verified by a classical example of 6:1 prolate spheroid, the results showed that γ-Reθ-CF transition model can better predict the transition position than the original version, and it also has good accuracy in predicting the drag characteristics. Besides, γ-Reθ-CF transition model can reflect the influence of crossflow effect at different angles of attack. On this basis, hull optimization design was carried out considering the crossflow effect, involving geometric factors including hull length, slenderness ratio and maximum diameter position. Compared with Goodyear airship with traditional ellipsoid hull shape, the drag reduction of optimized hull shape at 0° attack reached around 40%.