Aattapulgite (APT) was treated by 1% (v/v) HCl, H2SO4, H3PO4, HClO4 and H4P2O7 solution at a ratio of solid to liquid of 1:10. Poly(vinyl alcohol) / attapulgite (PVA/APT) nanocomposite films with different acids treated APT were prepared using film-casting method. The microstructures of the nanocomposite films were investigated using FTIR, SEM and XRD. The mechanical properties and water-resistance of the nanocomposite films were also tested. The experimental results indicate that the acid treated way can increase the dispersing capability of APT by dissolving the impurities and carbonate in the pore canal, and then APT can be dispersed better in PVA matrix，thus mechanical properties and water-resistance of the nanocomposite films have been significantly improved. Compare to nature APT, when adding APT treated with 1% (v/v) HClO4, the nanocomposite film has optimum performances, and the tensile strength, elongation at break and water resistance of the nanocomposite films have an increase of 29.3%, 74.9% and 32.2%, respectively.