The invention relates to a preparation method of sodium alginate for tissue engineering. The sodium alginate for tissue engineering is prepared by taking merchant food grade sodium alginate as raw materials, forming a gel by adsorbing the merchant food grade sodium alginate by active carbon, respectively soaking the gel in acid solution and alkaline solution, dissolving by using a chelating agent, filtering and dialysing the gel, finally precipitating the sodium alginate by using organic solution under the bacteria-free environment, and cooling and drying the sodium alginate. In the invention, the sodium alginate for tissue engineering is obtained by removing impurities such as impure protein, endotoxin and the like in the sodium alginate through the process.