By using organic montmorillonite (OMMT) as nano-filler, boric acid (BA) as chemical crosslinking agentto co-modify biodegradable polymer polyvinyl alcohol (PVA), and the PVA/OMMT/BA composites were prepared bysolution intercalation and flow forming method. The structure and morphology of the composite films werecharacterized by FT-IR, XRD and SEM. The effects of OMMT addition on thermal stability, mechanical properties andgas barrier properties of the BA crosslinking composite films were investigated systematically. Compared with pure PVAfilm, the PVA/OMMT/BA composite film with 4% OMMT show the best comprehensive performance, and themaximum thermal decomposition temperature increases from 258.4 ℃ to 361.6 ℃. And the tensile strength of the filmsincreases from 57.40 MPa to 108.15 MPa, while the elongation at break decreases from 130.84% to 77.60% .Additionally, the oxygen permeability is 21.0 cm³/(m²·d·0.1 MPa), which is 80.2% lower than that of pure PVA film.