The invention discloses low-whiteness pulp prepared by the alkaline cooking of a wheat straw raw material and a preparation method thereof. The fracture length of the low-whiteness pulp is between 5.5 and 7.2km, the folding resistance is between 20 and 60 times, the tearability is between 180 and 240 mN, and the whiteness is 55 to 60 percent ISO. The low-whiteness pulp can be taken as pulp of paper for high-quality life, paper for students and so on. The preparation method comprises the steps of alkaline cooking, oxygen delignification, chlorination, alkali treatment and so on. The low-whiteness pulp is obtained by the following steps: wheat straws are subjected to alkaline cooking to obtain high-hardness pulp the hardness of which is between 18 and 25 and is equivalent to a Kappa number of between 27 and 43, then the high-hardness pulp is subjected to oxygen delignification treatment by introducing oxygen and adding sodium hydroxide, or a pulp squeezing step and/or a disintegration step is then matched before the oxygen delignification, and then the chlorination and the alkali treatment are performed. The method prevents hypochlorite from performing degradation destruction on cellulose and hemicellulose in the pulp, saves the cost for enterprises, and ensures the high strength of the obtained pulp.