Abstract: The curves showing the relationship between the strength of the ultrahigh molecular weight polyethylene fiber bundle treated by atmospheric argon plasma and the epoxy resin interlaminar shear strength were investigated by varying technical conditions of low temperature and atmospheric argon plasma. The effect of argon plasma conditions on the fibers′ interface property was studied by comparing the changes of the strength of fiber bundle and the interlaminar shear strength. The influences of plasma treatment on bonding properties of fiber assemblies were further discussed by observing longitudinal microstructure of the treated tow and testing unidirectional properties of fiber reinforced composite which was made of the treated fiber tow by optimum technical parameters.