The work aims to develop a flexible film with excellent oxygen barrier performance and good application prospects in the field of food packaging. The PVA/MgAl-LDH composite film with excellent gas barrier performance was prepared by the casting method with biodegradable polyvinyl alcohol (PVA) as the film-forming substrate, magnesium-aluminum layered bimetallic hydroxide (MgAl-LDH) as the modifier, and citric acid as the cross-linking agent. The experimental results showed that with the increase of citric acid content, the hydrophilic property of the composite film gradually increased and the barrier performance decreased gradually. With the increase of MgAl-LDH content in the composite film, the hydrophobic property and barrier property of the composite film gradually increased. When the content of MgAl-LDH in the composite film was 1.5%, the mechanical properties of the film were the best, with a tensile strength of 42 MPa and an elongation at break of 16.7%. The gas barrier performance of the film with this MgAl-LDH content was also the best, with a gas permeability of 16 mL/(m2.24 h.0.1 MPa). In addition, the introduction of citric acid increases the number of hydrophilic groups inside the film, and the hydrophilic properties of the composite film are enhanced. MgAl-LDH can reduce the free volume inside the PVA film and enhance the mechanical and barrier properties of the PVA film.