Abstract: Objective To evaluate clinical efficacy of ¹³¹I treatment for thyrotoxic periodic paralysis. Methods 100 male patients with thyrotoxic periodic paralysis were divided equally into two groups, and treated with ¹³¹I or antithyroid drugs (ATD). They were followed up regularly for 3 years with the cure rate, the incidence of hypothyroidism, the recurrence rate of thyrotoxic periodic paralysis and the side effects, which included granulocytopenia, liver function damage and skin rash from medicinal herbs resource. Results The cure rate of ¹³¹I therapy and ATD therapy for thyrotoxic periodic paralysis is 80% and 52%, respectively. And there is significant difference between them (χ²=8.73,P<0.01). The group of ATD therapy has a higher recurrence rate of thyrotoxic periodic paralysis and more side effects (χ²=18.92, P<0.01;χ²=11.11, P<0.01). While the group of ¹³¹I therapy has a higher incidence of hypothyroidism (χ²=6.35, P<0.01). Conclusions ¹³¹I is preferable to effectively control the recurrent attacks of thyrotoxic periodic paralysis.