Numerical investigation of fluid–structure interaction (FSI) during parafoil gliding was conducted using the Arbitrary Lagrangian–Eulerian (ALE) method. The aerodynamic characteristics and structural responses of the parafoil under different angles of attack were systematically analyzed. Results demonstrate that significant flow separation occurs on the upper surface, which intensifies with increasing angle of attack, leading to enhanced lift and drag forces. Compared to the non- ballooning state, this inflated shape exhibits reduced spanwise length and increased cross-sectional thickness, which aggravates flow separation on both upper and lower surfaces. Consequently, the lift force decreases while drag increases, resulting in a deteriorated average lift-to-drag ratio.