Objective:To investigate the gene expression of sodium/iodide symporter(NIS) protein in papillary thyroid carcinoma(PTC) and the relationship between NIS and PTC. Methods:Thyroid tissue was obtained from 22 patients with PTC,12 samples of normal thyroid tissue(NT),7 samples of lymph node metastasis tissue(LN),and 12 samples of nodular goiter tissue(NG),respectively. The expression of NIS was evaluated by the Western blot technique. Results:NIS positive ratio in PTC and LN tissue was 77.3% and 85.7% respectively,higher than that in NT and NG. Difference between experimental groups was significant(P < 0.05). 16 samples of 17 NIS positive patients with PTC were mainly expressed in the cytoplasm,and only 2 samples were detected in the membrane. The difference was also significant(P < 0.05). Conclusion:The NIS protein in PTC was normally expressed,even over-expressed,and was mostly expressed in the cytoplasm rather than in the functional membrane,which related to the alteration of translation and modification caused by malignant tumor.