The invention discloses a carbon fixation meting method for marine organisms. The method specifically comprises the following steps that: classifying collected marine organism samples according to different species; decomposing into different tissues and organs; carrying out drying processing on different tissues and organs; calculating the wet mass ratio and the dry mass ratio of different tissues and organs of different species; measuring carbon contents before the sample is subjected to ashing; after the sample is subjected to ashing processing, measuring the carbon contents after the sample is subjected to ashing; calculating to obtain the carbon content of the wet sample before and after ashing; and according to existing biomass, estimating a marine organism existing carbon reserve, amarine organism fishing emigration carbon reserve, a marine organism deposited carbon reserve and a marine organism total carbon reserve. The method is simple and easy in operation, a situation of the storage carbon of the marine organism can be effectively estimated, meanwhile, the carbon fixation ability of different marine animals and the carbon deposition of the marine animals are researched,the species with high carbon fixation ability can be screened, and a scientific basis is provided for the modular construction, the carbon sink estimation and the operating management of a marine pasture.