The purpose of this in vitro experiment is to explose the effect of bleaching agent and mask agent on composite resin-enamel adhesive strength by means of shear test.The result showed:(1)bleaching agent could decrease adhesion of composite resin-enamel,but it is also related to the type of bleaching agent,the concentration of hydrogen peroxide and bleaching time.(2)Good quality mask agent,such as Bayer and 3M agent had no influence on composite resin-enamel adhesion.Therefore,clinically it is practicable to use 40%carbamide peroxide(in which the concentration of hydrogen peroxide is 14%),bleached for the limit of 10 min and thoroughly sprayed with water or covered with good quality mask agent and then finished with composite resin to complete the repair process.