In vitro digestion model was used to detect the bioaccessibility of 6 essential trace metals （including Cu， Fe，Mn， Zn， Co and V） and 5 harmful trace metals（including As， Cd， Pb， Al and Sr） in fresh and cooked seaweed （Porphyra yezoensis and Laminaria japonica）， with microwave digestion and inductively coupled plasma-mass spectrometry （ICP-MS） for measurement of total content of trace metals in the samples and residue， and the high-performance liquid chromatography coupled to inductively coupled plasma-mass spectrometry （HPLC-ICP-MS） for measurement of As and Cd species in the samples and chime. Results showed that 6 essential trace metals in two kinds of seaweed decreased after cooking， and their bioaccessibility in P. yezoensis were higher than in L. japonica. In addition， different trace metals exhibited different changes in the bioaccessibility for cooked L. japonica， with the highest bioaccessibility of Sr and the lowest bioaccessibility of Fe and Zn. The total content of As， Cd， Pb and Al in P. yezoensis was higher than that in L. japonica， and all of them decreased after the seaweed were cooked. Pb bioaccessibility in both cooked L. japonica and P. yezoensis were lowest （6.7% and 21.4% respectively）， while the bioaccessibility of Cd， As and Al was 77.4%， 82.1% and 57.8% respectively for L. japonica and was 74.6%， 71.7% and 67.5% respectively for P. yezoensis. A significant difference in the arsenic species in seaweed occurred during the gastrointestinal digestion， and some organic arsenic species may be transformed to be inorganic arsenic. Cooking would not change the As species in the seaweeds and the gastrointestinal juices， and the decreasing of total arsenic for the cooked seaweed may mainly include the dissolved organic arsenic. Content free inorganic cadmium Cd2+ in the fresh P. yezoensis and gastrointestinal juices could be significantly decreased after cooking. No matter for the fresh or cooked samples and gastrointestinal juices， no Cd2+ could be found in L. japonica. Present results may provide important information on the evaluation of nutritional value of essential trace metals and risk assessment of toxic trace metals in seaweed.