The invention relates to a stratospheric airship flight performance parameter estimation method and system. The stratospheric airship flight performance parameter estimation method comprises the steps: enabling an airship in a steady circling flight state; acquiring ground velocity, attitude angle information and position information of the airship; estimating flight performance parameters of the airship according to the ground velocity, attitude angle information and position information of the airship. According to the stratospheric airship flight performance parameter estimation method and system, which are provided by the invention, the accurate flight performance parameters, such as horizontal wind velocity, wind direction, airspeed, steady circling radius, circling period, circling angular speed, sideslip angle, attack angle and the like, can be computed by utilizing the ground velocity, position information and attitude angle information given out by a navigation system of the airship under an upper thin atmosphere environment; furthermore, the process is simple and is easy to implement; as long as main propeller rotation speed and yaw controlled quantity are constant, the airship can start the circling flight state; due to the circling flight, the airship has a constant altitude, and the wind speed and the wind direction are also constant, so that the airship is located under a constant wind field, and airship flight performance parameter estimation errors are reduced.