The invention discloses a sodium salt chemical ice bag and a preparation method thereof. The ice bag is composed of the following components in parts by weight: 40 to 50 parts of sodium nitrate, 10 to 20 parts of sodium borate, 20 to 30 parts of sodium sulfate decahydrate, 1 to 3 parts of sodium carboxymethyl cellulose, 1 to 3 parts of sodium silicate, 1 to 5 parts of sodium chloride, and 1 to 5 parts of sodium hydroxide. The preparation method comprises the following steps: precisely weighing the components according to the formula mentioned above, adding weighed sodium carboxymethyl cellulose into sodium borate, stirring, heating, stopping heating when the solution turns transparent so as to obtain a solution A; sequentially adding sodium nitrate, sodium sulfate decahydrate, and sodium silicate into the solution A under stirring, evenly stirring to obtain a solution B; adding sodium hydroxide into the solution B, evenly stirring, then adding sodium chloride, evenly stirring, when the solution becomes transparent, and packing the solution into bags. The provided chemical ice bag has the advantages of low refrigeration temperature and long refrigeration time.