The invention discloses a preparation method of corn starch adhesive through cannabis degummed waste liquor, which comprises the following steps: a, the preparation of carrier starch, b, the preparation of main starch, and c, the preparation of the corn starch adhesive. Corn starch is dissolved in warm water at 40 plus or minus 2 DEG C, and then catalyst FeSO4 is added. Cannabis degummed waste liquor is added till the pH value is 11.0 to 11.2, H2O2 is slowly added, and reaction is performed for 120min. Residual degummed waste liquor is added and stirred. Borax is dissolved in warm water at 40 plus or minus 2 DEG C, and then corn starch is added and uniformly mixed, and a small amount of tributyl phosphate is added, so as to perform defoaming. The carrier starch is added into the main starch while being stirred, stirring is performed for 30min, heat preservation is for 30min at 40 plus or minus 2 DEG C, and then a finished product is obtained after cooling. For producing 1 ton of adhesive, 166 Kg of corn starch, 260 Kg of degummed waste liquor, 0.22 Kg of FeSO4, 8.88 Kg of 30 percent H2O2, 2.33 Kg of borax, and 0.11 Kg of tributyl phosphate are required. The method is simple in processes and easy for industrialization, reduces the pollution of the cannabis degummed waste liquor, reduces the environmental management cost, simultaneously reduces the preparation cost of the corn starch adhesive, and increases the economic efficiency of enterprises and social benefit.