Abstract: Objective To investigate the value of ¹³¹Ⅰ therapy and the changes of the serum, urine contents of β₂-microglobulin(β₂-MG)in leukopenia in patients with Graves' disease before and after ¹³¹Ⅰ therapy. Methods Serum and urine β₂-MG contents (with radioimmunoassay), serum free triiodothyronine (FT₃) and free tetraiodothyronine (FT₄) lever (with chemiluminescence immunoassay) were determined before and after ¹³¹Ⅰ therapy. At the same time, measure blood ured nitrogen (BUN) and creatine (Cr) Results The cure rate, improvement, invalid, hypothyroidiam and total effective rate of ¹³¹Ⅰ therpy are 76.7%, 13.3%, 3.3%, 6.7%, 96.7% respectively. The serum and urine β₂-MG contents as well as the serum FT₃, FT₄ levels in the 30 patients before treatment were significantly higher than those in the controls (P<0.01). While leucocyte was significantly lower than those in the control (P<0.05). After 3 months treatment, their FT₃, FT₄ levels lower than before treatment (P<0.01),32-MG levels lower (vs before treatment, P<0.05), leucocyte increased (vs before treatments, P<0.05). After 6 months treatment, their β₂-MG,FT₃,FT₄ levels dropped to approaching normal (vs controls, P>0.05 and vs before treatments, P<0.01). Both BUN and Cr of the controls and before treatment groups have no big difference. The serum FT₃, FT₄ level was positively correlative to the β₂-MG (P<0.05). Conclusions ¹³¹Ⅰ therapy is an ideal treatment for Graves' hyperthyroidism, which have many advantages. β₂-MG could be used as a diagnostic indicator for leukopenia in patients with Graves' disease.