During the floating flight, the complex radiation-convection environment remarkably affects the flight performance and security of the stratospheric airship. The forced convection around the stratospheric airship plays an important role in the thermal behavior of the airship. Based on the hypothesis of pure heat conduction inside the airship, a three dimensional CFD model of stratospheric airships was developed and the thermal characteristics of the forced convective heat transfer of the airship were investigated. The distributions of the temperature of skins of the airship and the average temperature of the inner gas were calculated with the variation of the angle of the sun, the wind velocity and the angle of attack. Simulation results can be referenced for the accurate prediction of the thermal behavior of stratospheric airships.