Abstract: Objective: To evaluate the effects of Er:YAG laser irradiation on shear strength between glass ionomer cement and root surface dentine in the elderly.Methods: 20 elderly people(≥ 60) and 20 young people(≤20) teeth without caries and subfissure were selected from February to May in 2013 for this study and made into specimens with exposed root dentine by cutting the enamel and dentine around the mesial enamel-dentinal junction with a diamond bur.The teeth from the elderly people were randomly divided into group G1 and group G2 and teeth from the young people were randomly divided into group M1 and M2,each group contain ten teeth.Using defferent technique to prepare the root dentine:Group G1 and group M1 using Er:YAG laser irradiation,group G2 and group M2 using diamond bur preparation. Embedding each tooth in self-curing plastic,filling with GC Fuji Ⅸ GP CAPSULE glass ionomer cement after preparing the root dentine.All specimens were tested shear strength in universal testing machine after thermocycling.Results: The comprison of shear strength showes: group G1 >group G2, group M1 >M2, group G1> M1, group G2 > M2 (P < 0.05).Conclusions: Er: YAG laser irradiation can improve the shear strength between the dentin and ionomer cement; root dentin of elderly ones obtain higher shear bond strength to ionomer cement than the ones of the young.