Based on the analysis of present aircraft structural life index and its determination, the concept of Aircraft Structural Life Envelope (ASLE) is presented, as well as the approach to the establishment of ASLE. The schematic diagram of ASLE is given based on the total life and the time interval between overhauls. The establishment of ASLE will pave the way for the structural life ( i.e. fatigue life and calendar life ) supervision for individual aircraft.