As an environmental polymer compound, polyvinyl alcohol (PVA) shows excellent water-solubility, film forming and biodegradability properties. But the production, promotion, and application of PVA film are largely restricted by its poor water resistance. This study aimed to improve the water resistance of PVA films. Complete alcoholysis type PVA1799 was used to prepare water-soluble PVA packaging film, and the effects of chemical cross-linking treatment, heat treatment, cross-linking treatment combined with heat treatment on the structure and performance of the film were studied. Analysis showed that the moisture absorption rate of PVA film decreased obviously after adding saturated boric acid solution. The basic optimal temperature of boric acid bath was 70 °C and the optimal immersion time was 5 minutes. The water resistance of PVA film was improved by heat treatment. Through two-way combined processing, not only the chemical cross-linking but also crystalline structure occurred in PVA film. The number of hydrophilic hydroxyl groups within the molecule reduced, and the molecular chain arrangement became more regular and orderly. Compared with the single processing mode, the waterproof performance was greatly improved.