Due to the strong hydrothermal alteration, the original minerals of the kimberlite in Wafangdian, Liaoning Province were altered completely. It is quite difficult to identify such altered minerals under a microscope. To detect the mineral phases of the kimberlite, the X-ray powder diffraction technology is adopted. The result shows that, the major minerals of No.42 kimberlite pipe are serpentine, phlogopite and talc, with minor calcite, anatase, apatite, quartz, ilmenite, perovskite, sphene, magnetite and chlorite. The No.1 barren kimberlite at Shihuiyao is dominated by serpentine, phlogopite and dolomite, with a little calcite, anatase, apatite, talc, magnetite and chlorite.