Polyethylene terephthalate (PET) has been modified by Cr ion implantation with a dose range from 1×1016to 2×1017ions /cm2 using a metal vapor vacuum arc MEVVA source. The surface morphology was observed by atomic force microscopy (AFM). The Cr atom precipitation was found. The changes of the structure and composition have been observed with transmission electron microscope (TEM). The TEM photos revealed the presence of Cr nano-meter particles on the implanted PET. It is believed that the change would cause the improvement of the conductive properties and wear resistance. The electrical properties of PET have been improved after metal ion implantation. The resistivity of Cr ion implanted PET decreased obviously with an increase of ion dose. When the metal ion dose with 2×1017cm−2 was implanted into PET, the resistivity of PET could be less than 0.1 Ωm. But when Si or C ions with same dose are implanted PET, the resistivity of PET would be up to several Ωm. The result show that the resistivity of Cr ion implanted sample is obviously lower than that of Si- and C-implanted one. After Cr implantation, the surface hardness and modulus could be increased. The property of the implanted PET has modified greatly. The hardness and modulus of Cr implanted PET with dose of 2×1017/cm2 is 9.5 and 3.1 times greater than that of pristine PET. So we can see that wear resistance improved greatly. The Cr ion beam modification mechanism of PET will be discussed.