The modern stratospheric airship is required to reach the altitude of stratosphere safely and smoothly.The relationship between the airships altitude control and pressure difference control was analyzed.According to the characteristics of stratospheric airships, a feedforward altitude control approach was proposed.The simulation results showed that the feedforward controller had some limitations, and couldnt meet the goals for altitude and pressure control.Thus we put forward a pressure difference controller, and two solutions to resolve the integration problem of altitude and pressure controller.The final simulation results make known that the scheme of restricting the altitude controllers authority can ensure the airship to reach the required altitude safely and stably.