The analysis and design method of the sky-ground scaled similarity of aerodynamic characteristics for stratospheric airship were described in detail. The similarity criteria for the rigid and flexible models to complete the wind tunnel tests were given. Two kind of scaled models and wind tunnel test were completed. By analyzing the wind tunnel experimental data for scaled models, it was found that the aerodynamic characteristics of the stratospheric airship under different inflatable internal pressures were basically same, but the rigid body model was obviously different. The aerodynamic drag coefficient under flexible characteristics was significantly higher than that of rigid body, and even twice as high as that under zero attack angle, which lead to the essential changes of the rolling aerodynamic torque characteristics, such as stability and divergence. It has important engineering application value for evaluating flexible aerodynamic characteristics of stratospheric airship, especially under low pressure state. And it overcomes the disadvantages of using rigid body aerodynamic characteristics data or engineering estimation method in the airship overall design of "dynamic-resistance balance".