ObjectiveTo evaluate the effect of ethanol-wet bonding on caries affected dentin microleakage.Methods84 extracted human molars with coronal dentin caries were selected.The softened carious dentin was removed with a slow speed carbon steel, but CAD was reserved.The teeth were randomly distributed to six groups.Filling cavities with resin composite (3M,Z250).Observe the microleakage of six kind of conditions using staining test after 5 000 times thermocycling.Data were analyzed using SPSS 17.0 software, grade data were analyzed using Kruskal-Wallis test.ResultsAfter 5 000 times thermocycling, there was no significant difference between two subgroups of substrate condition in experimental hydrophobic adhesive group.Microleakage was significantly reduced in SB simplified ethanol wet bonding group than in SB traditional wet bonding group.Microleakage was significantly reduced in the SB experimental group than in the control group(P<0.05).ConclusionSimplified ethanol wet bonding technique can’t eliminate microleakage completely.However In the case of aging CAD bonding interface, the simplified ethanol wet bonding technique can reduce the microleakage in the SB group.