Shape optimization of a stractospheric airship was conducted with a gradient algorithm to reduce the aerodynamic drag. The total drag coefficient as the objective function was evaluated by solving the Navier-Stokes equations. The shear stress transport(SST)κ-ω turbulent model with transition criterion and the Realizable κ-ε full turbulent model were applied when solving the flow field in the optimization steps. The aerodynamic performance of the flow structure around these two optimized airships was thoroughly analyzed based on the flow field obtained through large-eddy simulation. The influences of the transition model and the full turbulent model on the optimized objective function and the hull shape itself were compared. It is found that aerodynamic performance of the optimized hull taking laminar-turbulent transition into account is obviously better than the other. The existence of the laminar region enables to change the shape of rear part of the hull and determine a better shape with smaller separation zone.