The invention discloses cotton fabric printing paste. The cotton fabric printing paste is prepared from the following materials in parts by mass: 75 parts of carboxymethyl starch, 13 parts of sodium alginate, 8 parts of nanometer silica, 4 parts of protein slurry; the carboxymethyl starch is prepared by fully mixing corn starch and potato starch with sodium hydroxide and chloroacetic acid, extruding with a screw extruder, spraying formaldehyde on the materials at the last half stroke of the screw extruder and finally drying, wherein a weight ratio of the corn starch, potato starch, sodium hydroxide, chloroacetic acid is 46 to 48 to 19 to 8; a mixture of the carboxymethyl starch and the nanometer silica is prepared by mixing the carboxymethyl starch with silica powder and then adding into deionized water, adding sodium hydroxide and methanol, performing hydrolysis and drying and purifying; the protein slurry is prepared by adding soybean protein to a sodium hydroxide solution with concentration of 0.25%, stirring at 48 DEG C at a constant speed for 20 minutes, then filtering the precipitate. The cotton fabric printing paste has the beneficial effects of good performance and low production cost.