Objective To investigate the iodine intake level and the prevalence of thyroid nodules in Harbin City,and to study the correlation between the concentration of urinary iodine and the prevalence of thyroid nodules.Methods In Harbin,18 communities were randomly selected and specimens were collected from fasting morning urine from 2015 to 2017.The urine iodine concentration (UIC) was detected by arsenic cerium catalytic spectrophotometry,and the thyroid nodule was examined by B ultrasound.Results A total of 2 552 residents aged (45.79 ± 12.06) years old agreed to participate in the study,including 371 males and 2 181 females.The median UIC in all participants was 159.8 μg/L,there was a significant difference in urine iodine frequency distribution among age groups (x2 =40.097,P ＜ 0.01).Furthermore,the median UIC in male was 166.6 μg/L,and in female was 156.2 μg/L.There was a significant difference in UICs between male and female (U =2.122,P ＜ 0.05).The prevalence of total thyroid nodules in all participants was 48.75％ (1 244/2 552),and the standardized rate was 40.55％.Significant difference in the detection rate of thyroid nodules was observed among age groups (x2 =114.922,P ＜ 0.01),and there was a positive and significant correlation between the detection rate of thyroid nodules and increasing age (xtrand =111.746,P ＜ 0.01).Furthermore,in male,41.24％ (153/371) had thyroid nodules,with standardized prevalence rate of 41.13％,and in female,50.02％ (1 091/2 181) had thyroid nodules,with standardized prevalence rate of 49.20％.Likewise,there was a significant difference in the detection rate of thyroid nodules between male and female(x2 =9.790,P ＜ 0.01).The detection rate of thyroid nodules in the iodine deficient population (urinary iodine was 0-＜ 100 μg/L) was 55.58％ (244/439),and the incidence of thyroid nodules in the iodine adequate or optimal population (urinary iodine was 100-＜ 200 μg/L) was 46.68％ (591/1 266).Conclusions The total iodine level of the population in Harbin City of Heilongjiang Province is at adequate level.The detection rate of thyroid nodules is high and it is increased with age.The detection rate of thyroid nodules is higher in female than male.Regular detection of urine iodine and adjusting iodine nutrition will help prevent thyroid nodules.