In this paper, the low-temperature plasma was applied to treat the surface of the fibers.The results show that the surface energy of the treated fibers increases greatly so that the fibers can be wetted very well by resin and the adhesion strength of the treated fibers to resin increases significantly.The mechanical characteristics of the PE composites are improved by the surface treatment of the fibers.In this paper, the mechanism of treatment has been discussed.The varieties of polar oxygen containing groups produced in the surface layer which form chemical bonding and the plasma etched pits spreading all over the surface of the treated fibers into which the resin penetrates to form the mechanical interlacing between fibers are the two reasons for the improvement.