Abstract: By determining the horizontal distribution of ²²⁶Ra in sediments of Xiamen Sea Area, it is found that the most silts from Jiulong River move to the offshore area along the main current direction of Jiulong River through the outside Xiamen Harbour and only a very small part of the silts enter the west Xiamen Harbour (i. e. the principal channel) with the residual current. The greater part of the silts do not enter the east-section of the west harbour but stop in the west-section of the harbour. This has effects on the channel of the west-section, not on that of the east -section. The results are in agreement with those obtained in other ways.