Abstract: Porphyra yezoensis hydrous pyrolysis in closed system at different maturity stages were carried out,and their hydrogenation generation characteristics were compared with those of plankton and single cell alga.Double-peaked hydrocarbon production rate was appeared with the temperature ascending in multi-cell benthic macro alga.Light oil was the main product in lower maturation period;gas-carried condensate oil reached its peak and the product rate of gaseous and liquid hydrocarbon was equivalent during maturation period.Gaseous hydrocarbon was dominated because of both the organic matter and liquid hydrocarbon pyrolysis during the high-matured period.The different kinds of alga have different models for hydrocarbon ge-neration and expulsion at different thermal evolution stages.For deoxidation reaction,the plankton alga occurred during the maturity stage while the single and multi-cell alga occurred during low-maturity stage.For the liquid products,the non-hydrocarbon was the main product for plankton and multi-cell alga in both low-maturity and maturity stages,while the asphaltene was the main product for single cell alga in the same stage.In the post-maturity stage,the aromatic hydrocarbon content arose in single-cell alga while the multi-cell alga had the most of saturated hydrocarbon product.The difference of family group for different kinds of alga can affect the resource assessment in certain degree.