Abstract: Calcium sulfate whiskers were used to modify the polyurethane-epoxy resin，and the influence of the pretreatment condition，the length and content of the whiskers on the adhesive properties of the polyurethane-epoxy resins was investigated. The modifying mechanism of calcium sulfate whiskers to the polyurethane-epoxy resin was discussed，too. The adhesive properties of the modified polyurethane-epoxy resin to aluminum alloy LY12 were improved when the shorter whisker pretreated with 1% KH-560 was added into the resins，whose RT peel strength rose by 27%，the 100℃ and -70℃ lap shear strength of the modified polyurethane-epoxy resins rose by 39% and 10%，respectively. The adhesive properties of the modified resins and the SEM images show that the modifying mechanism of the whiskers to the polyurethane-epoxy resin was crack deflexion.