The invention discloses a special finishing agent for dip padding finishing of a cotton fabric. The raw materials of the special finishing agent comprise, by weight, 5-15 parts of a phosphorus and nitrogen flame retardant, 2-9 parts of ammonium dihydrogen phosphate, 1-5 parts of boron phosphate, 0.2-1.3 parts of zinc nitrate, 0.1-1 part of fatty alcohol polyoxyethylene ether, 0.2-1.5 parts of polypropylene glycol, 15-25 parts of carboxymethyl cellulose, 0.5-2 parts of aminosilicon oil, 3-8 parts of maleopimaric acid, 0.2-0.8 part of guar gum, 3-12 parts of sorbitan monooleate, 0.3-2 parts of quinine, 0.1-1.2 parts of n-dodecyltrimethoxysilane, 30-100 parts of silica sol, 2-10 parts of an antibacterial agent and 300 parts of water. The special finishing agent for the dip padding finishing of cotton fabric can significantly improve the flame retardation property and the antibacterial property of the cotton fabric, and makes the cotton fabric washable and non-deformable.