Objective To explore the relationship between iodine and fluoride content in drinking water and the incidence of adult thyroid nodules in Cangzhou,Hebei.Methods According to the previous reports on iodine and fluoride levels in drinking water in Cangzhou,from November 2016 to January 2017,Cangzhou was divided into high iodine,low iodine,normal iodine and fluorine,low iodine and high fluorine,high iodine and high fluorine areas,and according to the different contents of iodine and fluorine in drinking water,high iodine and high fluorine area was further divided into high iodine and high fluorine 1 (iodine:743.30 μg/L,fluorine:4.27 mg/L),2 (iodine:119.31μg/L,fluorine:4.67 mg/L) and 3 (iodine:105.30 μg/L,fluorine:1.64 mg/L) subareas.Subjects who lived for 20 or more years and aged 30 or older,without serious disease and not taken iodized salt were selected.Palpation was used to examine the size,texture,mass,tenderness and mobility of the thyroid gland.The boundary,internal echo,blood flow and quantity of nodules were observed and recorded by color Doppler.Results The prevalence difference of thyroid nodules [36.8％ (629/1 710),32.8％ (636/1 938),25.1％ (427/1 700)] in high iodine,low iodine and normal iodine and fluorine areas was statistically significant (x2 =55.597,P ＜ 0.05).The prevalences of thyroid nodules in both high iodine and low iodine areas were higher than that of normal iodine and fluorine area (P＜ 0.016 7).The prevalence difference of thyroid nodules [43.3％ (749/1 730),39.8％ (712/1 790),34.9％ (623/1 785)] in high iodine and high fluorine 1,2 and 3 subareas was statistically significant(x2 =26.220,P ＜ 0.05).Compared with low iodine area,the prevalence of thyroid nodules [41.2％ (735/1 785)] in low iodine and high fluorine area was increased (x2 =6.288,P ＜ 0.05).Conclusions Both high iodine and low iodine can induce thyroid nodules.In water source areas with high iodine content,both high iodine and high fluorine are the factors inducing thyroid nodules.The prevalence of thyroid nodules in low iodine and high fluorine area is significantly higher than that of low iodine area.