Objective To understand the urinary iodine levels of pregnant women and children in Xiaochang County,and to evaluate the iodine nutritional status of this population. Methods From 2020 to 2022,300 people were randomly selected from 12 towns in Xiaochang County as the key monitoring population every year,including 200 school-age children aged 8 to 10 and 100 pregnant women.A total of 900 random samples of urine were collected in the three years.The urinary iodine levels were detected by arsenic cerium catalytic spectrophotometric method. Results In children aged 8-10,the median of urinary iodine was 252.8 μg/L in boys and 214.5 μg/L in girls.There was no statistically significant difference in the distribution of urinary iodine levels between boys and girls (χ²=3.682,P=0.303).There was statistically significant difference in the distribution of urinary iodine levels in children of different ages (χ²=24.180,P<0.001).There were 49 cases in early pregnancy,the median of urinary iodine level was 185.0 μg/L,with 14 cases (28.6%) of iodine deficiency (urinary iodine level < 150 μg/L) and 5 cases (10.2%) of iodine excess (urinary iodine level ≥ 500 μg/L).There were 158 cases in the second trimester of pregnancy,the median of urinary iodine level was 234.9 μg/L,with 48 cases (30.4%) of iodine deficiency and 18 cases (11.4%) of iodine excess.There were 93 cases in late pregnancy,the median of urinary iodine level was 258.6 μg/L,with 29 cases (31.2%) of iodine deficiency and 11 cases (11.8%) of iodine excess.There was no statistically significant difference in the distribution of urinary iodine levels among pregnant women of different gestational periods (χ²=7.906,P=0.251).There were statistically significant differences in the distribution of urinary iodine levels among children (χ²=57.091,P < 0.001) and pregnant women (χ²=72.040,P<0.001) in different years. Conclusion The iodine nutrition of pregnant women and children in Xiaochang County is favorable.