The objective of this study was to investigate the uniformity and penetration of surface modification into textile materials including fiber, yarn and fabric treated by atmospheric pressure plasma jet (APPJ). Exposure to helium/oxygen plasma at atmospheric pressure made improvement in the wettability, dyeability, adhesion of single fiber, yarn and woven fabric. The results showed that such a plasma jet was possible and effective in penetration of surface modification into textile structure. It can treat the whole surfaces of a single fiber, yarn filament in the treated parallel filament tow uniformly. For porous fabrics, rapid and efficient treatment on both sides of the treated samples was found to be ensured. And the degree and depth of penetration depended on the penetration of active species in plasma jet, which was affected by plasma parameters and materials structure. The former included treatment time, power, gas temperature, jet-to-substrate distance. The latter included number of twisting and fabric pore size. These findings would have important effects on industrialization of textiles treated by atmospheric pressure plasma jet.