Pentaerythritol was used as the plasticizer to prepare PVA films through solution casting method. The interaction between pentaerythritol and PVA was studied by FTIR. The crystallinity of raw PVA and modified PVA films was characterized by X-ray diffraction. The effect of the addition of pentaerythritol on the swelling properties, mechanical properties and optical properties of PVA films were investigated. The experimental results showed that the addition of pentaerythritol destroyed the hydrogen bonding in the PVA molecule and reduced the crystallinity of PVA. As the pentaerythritol content increased, the swelling property of the PVA films was significantly improved. The addition of pentaerythritol into PVA resulted in the increase of elongation at break, as well as the decrease of tensile strength. As the amount of pentaerythritol added, the optical performance of the PVA films was improved.