Abstract: Surface sediment samples were collected in May and June 2021,in the Jiulong River mangrove reserve and non-mangrove area.The iodine and organic carbon of the samples were analyzed.The results showed that,in the 13 samples,the iodine ranged from 3.7 to 24.8 mg·kg^-1,the difference among them could be as high as 7 times,with an average of 12.3 mg·kg^-1;the range of organic carbon was 16~45 g·kg^-1 and the average value was 30 g·kg^-1.Different types of samples were made sequentially:long-aged mangrove sediment>river dredging sediment>non-mangrove sediment> short-aged mangrove sediment.The concentration of iodine in the long-aged mangrove sediment with the highest content ranged from 15.7 to 24.8 mg·kg^-1,with an average of 19.2 mg·kg^-1,while the concentration of iodine in the short-aged mangrove sediment ranged from 5.5 to 6.9 mg·kg^-1,with an average of 6.2 mg·kg^-1,the difference was more than three times between the two types of samples.The highest organic carbon content was both 32 g·kg^-1 in the long-aged mangrove sediment and river dredging sediment,while the lowest content was 22 g·kg^-1 in the short-aged mangrove sediment.Basically,there was a positive correlation between organic carbon content and iodine content in different types of sediments,but the co-relaitonship was not significant.For the samples with the same organic carbon content,the iodine of long-aged mangrove sediment was significantly higher than that of other samples.