Abstract: Reefed parachute can achieve an obvious load reduction. To study the influence of reefing ratio on inflation performance and drag area, the fluid-structure interaction numerical method was proposed to study the influence of reefing ratio. Firstly, the fluid-structure interaction numerical calculation of an un-reefed ringsail parachute was conducted, and its feasibility was verified by test results. Secondly, the inflation stage of reefed parachute including five reefing ratios from 13％ to 28％ was simulated. The changes of canopy shape, opening load, drag area and tension of reefing line under different reefing ratios were studied. The corresponding relationship formulas were fitted. The results show that the inlet open speed is not affected by the reefing ratio, but the first open time points of inlet and vent are affected by the reefing ratio. The reefing ratio is in quadratic relationship with reefing diameter ratio and drag area. And the reefing ratio is in linear relationship with the maximum opening load. The tension of reefing line is the maximum when the reefing ratio is 19％. These results can provide reference for the selection of reefing line and optimization design of reefing ratio.

Key words: Reefing ratio, Inflating performance, Drag area, Fluid-structure interaction, Ringsail parachute