Objective:To investigate the effect of operation for hyperthyroidism assoiciated with hypokalemic periodic paralysis (HPP).Methods :We retrospectively analysed the clinical data of 121 cases of hyperthyoidism associated with HPP. Among them 81 patients received subtotal thyroidectomy after taking Lugol solution for 2 weeks；40 patients received nonoperative therapy.Results:The plasma potassium，T3,T4,TSH and BMR levels of patients who received subtotal thyroidectomy were all normal 1 week postoperatively, Only 2 patients suffered symptoms of relapse at follow up of 0.5-10 years, with cure rate of 97.5％; 8 of the patients who received nonoperative therapy recovered, with cure rate of 20.0%.Conclusions:Operation for hyperthyroidism associated with HPP could cure HPP and hyperthyroidism simultaneously.The therapeutic efficacy of operation is rapid and stable, and is markedly better than that of nonoperative therapy.