Laminaria japonica was collected from the coast of Qingdao in April, 1995. Based on a first paper (determination of the content of organic iodine in seaweed, Acta Hydrobioloica Sinica，1999, 23(5): 489-493), the existing states and content of organic iodine in seaweed were investigated by paper chromatography and infrared spectrum. The result shows that iodine in Laminaria japonica occurs as organic iodo-compounds and inorganic iodine. The main organic iodo-compounds are amino-acids derivative and non-amino-acids derivative. 51% of total organic iodine compounds are iodo-amino acids and their main existing state is 3, 5-diiodotyrosine. 49%o of iodo-amino acids existed in free state amino acids and another 2% in combined state. Infra-spectrometry was used to confirm the structure groups of iodo-amino acids from fresh Laminaria japonica.