Objective To evaluate the effectiveness of the Otago exercise on frailty in institutionalized residents. Methods Seventy-six institutionalized residents were assigned into an intervention group of 35 and a control group of 41, receiving either 3-month of group Otago exercise intervention or routine care, respectively. The effect was measured after 3 months of intervention. Results There were no significant differences in muscle strength of the lower extremities, balance ability and frailty between the two groups before the intervention （P＞0.05 for all），whereas the mobilization ability of the intervention group was poorer than the control group before the intervention (P<0.05). Mobilization ability, muscle strength of the lower extremities, balance ability and frailty were significantly improved in the intervention group after the intervention and were also better compared with the control group (P<0.05 for all). Conclusion The Otago exercise can effectively improve muscle strength of the lower extremities, balance ability and mobility of the elderly in elder-care institutions, thus to ameliorate frailty.