With eight four methyl siloxane (D4), 1,3 -bis(3 -aminopropyl )-1,1,3,3 -tetramethyl disiloxane by bulk polymerization, the preparation of ammonia propyl sealing side polysiloxane (ASO - 2), then its and isophorone isocyanate (IPDI) and polyethylene glycol 1000 (PEG - 1000) and triethanolamine (TEOA) preparation of polyurethane pre polymers (PU) reaction, was IPDI type cationic waterborne polyurethane modified amino silicone finishing agent (PUASO - 2). Using IR, FE - SEM, nanometer particle sizer PUASO - 2 and its emulsion were studied. Research shows that: the outer emulsion prepared PUASO - 2 emulsion (PUAS - 2) particle distribution, the average particle size of 38.64 nm.When the polyurethane PU content of 20%, for cotton twill and plain cotton processing, respectively, after finishing the bending rigidity of 954 mN,525 mN, crease recovery Angle is 178.86 °and 272.81 °; Compared with not finishing two kinds of cotton fabrics, the growth of 23%, 26% and 37%,35% respectively。With ASO - 2 compared to the two kinds of cotton fabrics after finishing，PUAS - 2 to sort out the white degree of two kinds of cotton fabrics after wb increased to 78.18 wb and 73.45 wb from 81.13 wb and 76.64 wb, fabric crease recovery Angle increased by 140.44 ° and 205.65 ° respectively to 174.71 ° and 269.02 °, and static water absorption time increased to 1.78 s to 2.68 s, softness were slightly down.