Abstract: The M/G ratios of the sodium alginate extracted from the kelp and gulfweed were 1.62 and 0.91 respectively. Afterthe heat-proof testing, it was found that the sodium alginate viscosity with M/G ratio 1.62 began decreasing at 60℃, but thesodium alginate’ viscosity with M/G ratio 0.91 would not decrease until 80℃.Ultraviolet radiation would have at so a degradationeffect on sodium alginate and it would became obvious with the time. The degradation ratio of the 1% sodium alginate aquatic solutionwas thirteen times that of the dry sodium alginate with water content 13.54%.

Key words: sodium alginate, M/G ratio, viscosity, heat-proof, ultraviolet radiation