Mixed type diamonds occur in porphyritic Kimberlite tube in China. It a- mounts to 6% of the total diamonds yield. Mixed type crystal of diamond is composed mainly of type I molecules and a less amount (about third to fif- th of the crystal) of type I molecules. The crystals are colorless, transparent and small octahedra (most sized mm).On the ultra-violet transparent pho- tographs, within the crystal, shows small black area of opacities, and outside of this area shows white area transparent under emissive ultra-violet light (wa- velenth 2370A).On the ultra-violet spectrogram, absorption edge of the black area is between 2916A—2970A，but the white area transmits ultra-violet light beginning at 2230A，Its representing forbidden band width is 5. 51 ev. On the infrared spectrogram, the black area shows strong absorption at 1175,1282， 1370 cm-1 and week absorption at 1100 cm-1 that they were lead. by rich, bi- nitrogen and poly-nitrogen; But the white area have no absorption peak lea- ding by impurities of nitrogen. Therefore, in a mixed type diamond, local small black area marks type , I，and vast white area indicates type II.