Objective To study the effects of different level of iodine nutrition on the thyroid function in women of reproductive age. Methods A total of 100 (50 from each) women of reproductive age but not pregnant were collected from iodine deficient and adequate areas. The questionnaire was obtained individually with items concerning personal history of thyroid diseases, goiters and category of edible salt and drinking water based on the project design. The household salt and drinking water were collected for measuring iodine content, and blood samples were obtained for TSH, FT4 and FT3 testing. Results The coverage of iodized salt and the median level of urinary iodine in iodine deficient women(72.0% and 95.5 μg/L) were obviously lower than that in iodine sufficient women(100.0% and 167.4 μg/L, χ2=16.28, U = 632.00, P < 0.01). Median level of serum TSH in iodine deficient women (2.56 m U/L) appeared in an increasing tendency compared to the iodine sufficient women (1.88 mU/L), but there was no significance (U=990.50, P > 0.05). Serum FT4 mean level in iodine deficient women [(14.7±2.0) pmol/L]was lower than that in iodine sufficient women[(17.0±3.8)pmoI/L, t=3.76, P<0.01]. There was no difference in serum FT3 between two group women[(5.1±1.4), (4.8±0.5)pmoI/L, t = 1.59, P > 0.05]; but FT3/FT4 ratio in iodine deficient women(0.33±0.04) was markedly higher than that in the iodine sufficient women(0.30±0.04, t=3.13, P<0.01). The percentage of thyroid dysfunction in iodine deficient women[20.0% (10/50)]was higher compared with the iodine sufficient women[8.0%(4/50)], but without significance(χ2=2.99, P>0.05). Conclusions Iodine deficiency is a primary cause leading to hypothyroid in women of reproductive age. Long term of iodized salt usage is an efficient way to correct iodine deficiency.