Abstract: ased on the H.G. Heinrich's theory of parachute opening dynamics,this paper considers the effects of vent, crown cloth area with large porocity, and porocity at the middle and lower portions of the canopy on parachute opening force. In continuity equation for calculation Filling time of parachute canopy the variation of drag area in process of canopy inflation is calculated by using the non-linear drag area variation curves. The initial parachute drag area during the inflation of parachute canopy is also considered. The constant inlet diameter is assumed and equals to (4(CA)0/ C(st)π)(1/2) during the initial phase of parachute inflation. The computation example shows that the results of calculation are in agreement with the measured data satisfactorily.