Abstract: A deep understanding of the fluid-structure interaction (FSI) problem of the parafoil under trailing-edge deflection is crucial for the maneuvering and landing design of large parafoils’ precision airdrop system. Based on the ALE (arbitrary Lagrangian Eulerian) algorithm and the penalty coupling method, the FSI modeling of parafoils under trailing-edge deflection is firstly proposed, then the structured ALE (S-ALE) method and the transient nonlinear dynamics solver are used to simulate a single cell 3D model of the parafoil under trailing-edge deflection, and the flow separation phenomenon due to the trailing-edge deflection is captured. The FSI characteristics of the parafoil under both single and double deflections are simulated and analyzed. The structural and surrounding flow fields evolution in the time domain are obtained, as well as the time history profiles of various parafoil aerodynamics. It is found that there is a delay in the manipulation under trailing-edge deflection. Finally, the simulation results are verified by a wind tunnel test, which suggests the efficiency of our method. The present results provide good support for the design and application of large parafoils.