The invention discloses a technique capable of improving the stability of printing and dyeing grade sodium alginate. The technique comprises the following steps: soaking brown seaweed, carrying out primary washing, digesting, diluting, filtering, calcifying, decalcifying, carrying out secondary washing, and dehydrating, so that alginic acid is obtained; then carrying out solid phase neutralization reaction to generate sodium alginate, adding a solid preservative, pelletizing, drying, cooling, smashing, adding a liquid preservative and a solid complexing agent, cooling, and packaging the finished product. The technique disclosed by the invention has the advantages that the stability of sodium alginate can be greatly improved, storage time of sodium alginate solid and glue solution thereof can be prolonged, and production cost is saved for a printing and dyeing factory.