To achieve a high viability by minimizing thawing damage, ice crystallization must be reduced in the process of thawing. Thermophysical properties of suspensions of Porphyra seriata, Undaria pinnatifida, and Sargassum fulvellum were measured to determine the optimal thawing conditions in the thawing process for species conservation of sea algae. The range of final thawing temperature was ?2.49 ~ ?0.50°C at thawing speed 1.25°C/min and 2~3°C at 1.5~2.0°C/min, and thawing was completed at temperatures above 3.0°C, enabling the removal process of cryoprotectant. The optimum thawing speed with the minimum thawing time was 0.75~1.0°C/min, and the latent heat of thawing was Undaria pinnatifida 128.37 J/g, Porphyra seriata 118.53 J/g, and Sargassum fulvellum 94.42 J/g, which can be useful for the design and manufacture of algae cryopreservation system. From the change of enthalpy, entropy and free energy according to each thawing rate, the optimum thawing rate for recrystallization temperature pan and viability improvement is suitable over Porphyra seriata, Sargassum fulvellum, Undaria pinnatifida 0.75°C/min, 1.0°C/min, 1.5°C/min respectively. From the results of the thawing process, the optimal method of freezing-thawing process of seedlings for aquaculture will be set up to in...