Laminaria japonica was collected from the coast of Qingdao from April to July,1995. Determination of the iodine contents of different parts in the same sample by an iodine ion-elective electrode showed that iodine was distributed throughout Laminaria japonica and could constitute 0.133%o of fresh weight. The iodine contents varied greatly within the same sample. The frond was richer in iodine than the stipe, especially in the top of frond, whose contents could reach 0.183% of fresh weight. This distribution characteristics relates to the plant metabolism. The more active metabolism some parts of Laminaria japonica have, the more iodine they accumulate.