Cassava starch (CS)/poly(vinyl alcohol) (PVA)/ kaolin clay (KC) nanocomposite films with high mechanical and barrier properties were prepared by casting film. Based on the CS/PVA matrix, the effects of KC content on the starch/PVA/KC nanocomposite films were investigated. X-ray diffraction results demonstrated that the CS/PVA/KC nanocomposite films exhibited KC good dispersion in the polymer matrix. FTIR spectra showed that the molecular interactions were enhanced in the CS/PVA/KC films with higher PVA content. The maximum tensile strength and elongation at break for the CS/PVA/KC composite films were 18 MPa and 330%, respectively. The CS/PVA/KC composite was applied to extend the shelf-life of banana and results showed that the good shelf-life of banana was accepted. The CS/PVA/KC composite film is a promising material for high barrier food packaging.