For the aircraft with two engines, the airworthiness regulation requires that the aircraft should have the capability to restart the engine at a suitable altitude, airspeed and engine condition when one engine failed. In order to show compliance to the regulations, the manufacture should conduct engine air start envelope extension flight test. The engine air start envelope flight test is a high risk, tough and many complex factors involved flight test. Taking a reference to some aircraft,this paper expounds flight test content analysis, flight test preparation, flight test organization and implementation, flight test results and so on, and summarizes the flight test experience in a systematic manner. Especially with regard to the air-ground decision-making mechanism, this paper summarizes and analyzes the specialized knowledge and role definition of test pilot, flight commander, flight test engineer, discipline engineer, and design engineer. It was a powerful guarantee for the test that all the participants monitor the aircraft status in real time and interpret the validity of the test sites. This successful organization and implementation of engine air start envelope extension flight test could provide an important reference to other type of aircraft.