The present invention discloses an all cotton digital printing textile slurry and a preparation method thereof, and belongs to the technical field of textile slurries. The all cotton digital printing textile slurry comprises, by weight, 80-88 parts of water, 1-3 parts of sodium alginate, 3-5 parts of sodium bicarbonate, 5-9 parts of urea, and 2-4 parts of sodium sulfate. The preparation method comprises: at a room temperature, at a rotation speed of 800-1000 rotation/min, taking 80-88 parts of water, adding 1-3 parts of sodium alginate, carrying out mixing stirring for 5-10 min, adding 5-9 parts of urea, continuously carrying out mixing stirring for 5-10 min, adding 2-4 parts of sodium sulfate, carrying out mixing stirring for 4-5 h, finally adding3-5 parts of sodium bicarbonate, carrying out mixing stirring for 2-3 h, and standing. According to the present invention, with application of the all cotton digital printing textile slurry, the printing is clear, the color reduction degree is good, the color fastness is good and can achieve more than grade 3, the whole preparation process is simple and is easy to control, the equipment investment is low, the cost is low, and the yield is high.