Abstract: Theoretical analysis is done for exploring speed-compensated reefing character of C-9 canopy used by ACES Ⅱejection seat. The reasons that opening shock is reduced at high speed and minimum safe altitude is not lowered at low speed after using reefing technics of recovery parachute are analysed. The character of chinese-built HTY-4 ejection seat with imaginary reefed recovery parachute JS-13 is estimated. If reefed drag area is equal to 20 square metre and time reefed equal to 10 second, the opening shock can be decreased by fourty percent at 3000 metres altitude. Selective principle of reefed drag area and time reefed is discussed.

Key words: recovery par achute, ejection seats, drag