Abstract:    Accurate airspeed and altitude are the basis for flight testing and ensuring flight safety. The latest airworthiness standard for civil transport airplane requires airspeed system should be calibrated in the full envelope of the airplane. The speed of the airplane on the ground roll stage and stall process is rapidly changing, and traditional airspeed calibration method is only applicable for stable state. This paper introduces the principle of DGPS method, using the relationship between DGPS height difference and the pressure height difference, to obtain the results of airspeed system position error under non steady state conditions. And this method has successfully applied on domestic regional airplane flight tests.