The silicone-modified polyurethane prepolymer was synthesized by step-growth polymerization of isophorone diisocyanate with polypropylene glycol, organosilicone, glycerin polyether, glycerin polyether and dimethylol propionic acid. After four kinds of silicone-modified polyurethane with different organic silicon content were obtained and then be emulsified into four inds of different concentration emulsion. The silicone modified polyurethane emulsion was applied in cotton finishing and the performances of treated and untreated fabrics were tested. When the amount of finishing agent is 100g/L, the silicone mass fraction of the finishing agent is 6%, the cotton fabric have the best comprehensive performance. The smoothness, softness and thermal property are greatly improved. The breaking strength of cotton fabric treated with this agent achieves 725.3N, which increases by 27.35% comparing to that of the untreated fabric. Urgent elastic recovery angle and gentle elastic ecovery angle of treated fabric reach 218° and 230° respectively, which increase by 21.11% and 12.20% respectively.