Abstract: The change of the molecular weight parameters of sodium alginate at normaltemperature and heat acceleration was investigated by high performance gel chromatography andviscometry.The results showed that the decrease in viscosity at normal temperature for a week couldapproximately be estimated from the data of heat acceleration at 40℃ for one day.In storage,thedecrease of Mn of sodium alginate was higher than that of Mw,It indicated that the lower molecularchain sequences formed in the process were the major factor influencing the molecular weightparameters.The molecular weight distribution was gradually extended with the prolongation ofstorage. The heat acceleration would decrease the storage stability of sodium alginate. Nitrogen andvacuum as protective atmosphere would not improve the viscous stability of sodium alginate in storage.