The aim of the present study was to explore the influencing factors of urinary iodine concentration (UIC) and the relationship between iodised salt concentration and UIC in order to give suggestions for the surveillance of iodine nutrition status. For this purpose, a multi-stage cluster sampling technique was employed in the present cross-sectional study. Correlations between UIC and salt iodine concentration were evaluated by Spearmen's correlation analysis. Risk factors of having a lower UIC were identified by logistic regression analysis, and the equations of UIC and salt iodine concentration were fitted by curve regression analysis. The median UIC was found to be 162·0 (25th–75th percentile 98·2–248·6) μg/l. The UIC was correlated with salt iodine concentration (Spearman's ρ = 0·144, P< 0·05). The multiple logistic regression analysis found the following influencing factors for having a lower UIC: age (OR 0·98, 95 % CI 0·98, 0·98, P< 0·05); sex (OR 0·81, 95 % CI 0·71, 0·92, P< 0·05); education level (OR 0·87, 95 % CI 0·83, 0·90, P< 0·05); status of occupation (OR 0·91, 95 % CI 0·86, 0·96, P< 0·05); occupation (OR 1·03, 95 % CI 1·00, 1·05, P< 0·05); pickled food (OR 1·24, 95 % CI 1·08, 1·42, P< 0·05); salt iodine concentration (OR 1·03, 95 % CI 1·02, 1·03, P< 0·05). The curve regression analysis found that UIC (y) and salt iodine concentration (x) could be expressed by the following equation: y= 1·5772x
1·4845. In conclusion, the median UIC of individuals in Zhejiang Province falls within optimal status as recommended by the WHO/UNICEF/International Council for Control of IDD. To maintain optimal iodine nutrition status, salt iodine concentration should be in the range of 16·4 to 34·3 mg/kg.