Objective To investigate the proliferation effects induced by triiodothyronine (T3) in thyroid cancer cell lines,including follicular thyroid carcinoma cells (WRO),interstitial thyroid cancer cells (ARO) and papillary thyroid cancer cells (FB-2) and relationship with the thyroid receptor.Methods Different concentrations of thyroid hormone T3 inter acted on the three thyroid cancer cell lines,detected by MTT assay,achieved effective biological dose.To detect proliferation rates in all the cell lines using MTT assay,under the effective biological dose.RT-PCR and Western blot were used to detect the mRNA and protein expression of thyroid receptor.Results Cell proliferation induced depend on different concentrations (10 nmol/L,100 nmol/L and 1 μmol/L) thyroid hormone T3 in thyroid cancer cells FB-2,the proliferation rates were (128.78±0.31) ％,(171.94±0.40) ％,(178.04±0.14) ％,had dose-dependent relationship,which was the most effective physiological dose of 100 nmol/L,cell proliferation was significantly in WRO and ARO under 100 nmol/L[(149.06±0.06) ％,(158.87±0.03) ％],obviously in FB-2 [(167.92±0.08) ％].The expression in mRNA levels of thyroid receptor subtype TRα1 in WRO cells was more,low and no expression in the FB-2 and ARO,did not protein expression,mRNA and protein of subtype TRβ1 expressed in FB-2 and WRO cells,while expressed very little in ARO cells.Conclusion Thyroid hormone T3 can induce thyroid cell proliferation and expression of TRβ1 is relatively important.