Objective:To evaluate the microtensile bond strength changes and patterns of fractures of the bonding interface after dentine surface treatment with carbodiimide-ethanol solution .Methods:1-eth-yl-3-(3-dimethylaminopropyl) carbodiimide (EDC) dissolved in ethanol was diluted into different con-centrations of 2, 1, 0.3, 0.1 and 0.01 mol/L EDC-ethanol solutions.Twenty-eight caries-free extracted human third molars were ground metallurgically to prepare flat occlusal mid-coronal dentin surfaces and etched with 35%( mass fraction) phosphoric acid gel .Then they were treated with EDC-ethanol solution for 60 s before the bonding procedure and randomly divided into five experimental groups corresponding to the tested EDC-ethanol concentrations .The ethanol treated and no pre-treated surfaces were used as con-trols.Single Bond 2 adhesive was applied and resin composite disk was stacked on the treated dentine surface .The teeth with resin composite disks were stored in water at room temperature for 24 h and then sectioned longitudinally to produce stick specimens for microtensile bond strength test .Fracture patterns were observed with a stereomicroscope .Results:The dentin surfaces pre-treated with 2 mol/L [ (22.17 ± 13.31) MPa] and 1 mol/L [(45.31 ±17.80) MPa] EDC-ethanol solutions resulted in statistically sig-nificant lower bond strength value ( P<0 .05 ) .Increasing numbers of fracture pattern at the resin-dentin interface were also found in this two groups with percentages of 81 .2%and 41 .3%respectively .No sig-nificant difference was observed in the groups with 0.3, 0.1, 0.01 mol/L EDC surface treatment ( P>0.05).Conclusion:No significant difference of immediate bond strengths was found in the 0.3, 0.1, 0 .01 mol/L groups compared with the control group .EDC-ethanol solution surface treatment with con-centrations of 2 mol/L and 1 mol/L resulted in decreasing of the bonding strength .