Based on the reaction of oligomer polyester polyols with isocyanates, a polyurethane adhesive is synthesized with strong adhesion and cooking resistance, which can be used for high barrier composite packaging films, followed by an exploration into the effects of different reaction conditions on the properties of polyurethane adhesives and composite films. Research has found that the initial viscosity of the main agent is positively correlated with the reaction temperature. The higher the R value (the ratio of the amount of isocyanate groups to hydroxyl groups), the higher the initial viscosity and average peeling force of the composite film will be. However, when the R value is too high or the proportion of trialcohol to total alcohol is too large, the synthetic polyurethane adhesive tends to gelation. The composite membrane prepared under optimal conditions is characterzied with a water permeability of 1.05 g/(m2·d), an oxygen permeability of 0.62 cm3/(m2·d), and an improved high-temperature retort resistance performance.