Abstract: The diffusion kinetic models established based on Fick's second law for polysaccharides from Porphyra yezoensis of both spherical and slab geometries were investigated in this paper.The polysaccharide concentrations in the Porphyra yezoensis soup were measured at different immersing temperature and different time.Results showed that the dissolution of polysaccharides from Porphyra yezoensis in the spherical model was significantly higher than that in the slab one.The polysaccharide dissolution rates of 62.07% and 64.05% were gained at 363.15 and 373.15 K for 20 min.Statistical results suggested that the kinetic model calculation values coincide well with the experimental data.And a series of kinetic parameters were gained.The apparent kinetic constants and diffusion coefficients both increased with temperature. The apparent activation energy were 5.984 k J/mol and1.406 k J/mol in the spherical and slab models, respectively. The relative yield of the polysaccharide dissolution was in accordance with exponential model.The kinetic models established the theoretical foundation for the optional immersing process for Porphyra yezoensis polysaccharides.