Abstract: Film morphology and molecular orientation of N-β-aminoethyl-γ-aminopropyl polysiloxane(ASO-1) on cotton fiber were investigated by field emission scanning electronic microscope(FE-SEM) and X-ray photoelectron microscope(XPS).The experiment results indicated that the ASO-1 formed a uniform,some smooth film on the treated cotton fiber surface,especially as the working distance(WD) of FE-SEM is more than 200 nm.The XPS analysis showed that most of the N atoms from amino functional polysiloxane were fixed onto the interface between the cotton fiber and ASO-1.All of these suggests that the molecular orientation of ASO-1 on natural cotton fiber substrate is in such a manner that the silicon methyl groups project outward into air,while Si—O dipole bonds as well as amino groups point to the fiber interface.