Abstract: Objective: To investigate the clinical effect and safety of iodine-131(¹³¹I) in the treatment of Graves disease(GD) complicated with leukopenia.Methods: Sixty-six cases of GD complicated with leukopenia were treated by ¹³¹I,and the levels of free triiodthyronine(FT3),free thyroxine(FT4),leukocyte and the curative effects were analyzed retrospectively.Results: The levels of FT3 and FT4 at 3,6 and 12 months after ¹³¹I therapy reduced markedly(P<0.01),but there was no significant difference among FT3,FT4 or leukocyte at 1 month after ¹³¹I therapy(P>0.05).After 6 months' treatment,the GD in 43 cases were cured,the leukocyte in 60 cases returned normal and 6 cases improved.Conclusions: After the therapy of ¹³¹I,most of GD patients complicated with leukopenia are cured or turn better.¹³¹I therapy is effective and safe for the treatment of GD complicated with leukopenia.