Objective To understand the iodine nutrition status and the changing trend of the key population in the Tongnan district of Chongqing to provide support for adjusting scientific iodine supplementation intervention strategies. Methods From 2016 to 2020

the town streets under the jurisdiction of the Tongnan district were divided into 5 areas（east

west

south

north

and middle）. One township（sub-district） was randomly selected from each area. A total of 20 pregnant women and 40 non-boarding students aged 8-10 years from 1 elementary school were selected from each township（sub-district） as the study subjects. Urine samples and salt samples were collected from the subjects to detect urinary iodine and salt iodine levels. Thyroid volume was measured by B-mode ultrasound in children in 2018 and 2020 to calculate thyroid enlargement rate. Results From 2016 to 2020

the coverage rates of iodized salt in children’s families were 100.00%

99.51%

100.00%

100.00%

and 99.50%

respectively. The consumption rates of qualified iodized salt were 97.00%

96.55%

98.00%

94.50%

and 94.50%

respectively. From 2016 to 2020

the coverage rates of iodized salt in families of pregnant women were 100.00%

99.00%

100.00%

100.00%

and 100.00%

respectively. The consumption rates of qualified iodized salt were 96.00%

88.00%

95.00%

95.00% and 93.00%

respectively. The median urinary iodine in children from 2016 to 2020 was 185.21 μg/L

198.50 μg/L

188.52 μg/L

188.80 μg/L

and 214.61 μg/L

respectively

and the difference was statistically significant（P<0.05）. From 2016 to 2020

the median urinary iodine of pregnant women was 158.60 μg/L

160.80 μg/L

188.52 μg/L

151.95 μg/L

and 130.01 μg/L

respectively

and the difference was statistically significant（P<0.05）. The thyroid enlargement rate of children in 2018 and 2020 was 2.50%

and there was no significant difference in thyroid enlargement rate between children of different years

gender

and age（all P>0.05）. Conclusion The iodine nu-trition level of the key population in the Tongnan district is at an appropriate level

and there are different degrees of iodine deficiency and iodine excess. It is necessary to strengthen the monitoring of iodine nutrition status and targeted intervention.