The structures of diamonds implanted with B and N ions have been studied by EPR and electron diffraction. The relationship between the spin density and the dose implanted is given and electron diffraction patterns are shown. The results of EPR and electron diffraction experiments show that the structure of diamond will be changed as implanted dose increases. The amorphous form of diamond can be formed when the doses are equal to and larger than 1–3 × 1015N+/cm2. The wear resistance of diamonds implanted at certain dose will be increased.