Abstract: Objective: To evaluate the effect of different energy densities of Nd:YAG laser irradiation on the dentin bond strength. Methods: Thirty-six intact third molars were randomly divided into three groups after the enamel were removed, The three groups are control group, low energy density group(1w, 85J/cm² ) and high energy density group(4w, 350J/cm²) . After the corresponding surface treatment, each group was divided into two sub-groups in order to evaluate the bonding strength of both self-etching adhesive (G-Bond, GC) and total etch adhesive (Single Bond 2, 3M ESPE). The dentin surfaces were observed by SEM and LSCM. Results: After irradiated by low energy density laser, the bonding strength of total etch adhesive was stable and that of self-etch adhesive decreased. However, after high energy density laser irradiation, the bonding strength of self-etch adhesive was maintained and that of total etch adhesive decreased. Conclusion: After low energy density laser irradiation, total etch adhesive will get more stable dentin bond strength. While after high energy density laser irradiation, self-etch adhesive will be better.