Abstract: Due to the strong hydrothermal alteration, the original minerals of the kimberlite in Wafangdian, Liaoning Province have been 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. The No. 9 barren kimberlite dyke is composed of mainly calcite and quartz, with some chlorite and barite. The No. 51 kimberlite pipe consists of mainly serpentine and phlogopite, with uneven calcitization and common dolomitization, also with some anatase, talc, magnetite, chlorite, apatite, ilmenite and quartz. The No. 30 poor ore sample is seriously weathered, with main mineral of montmorillonite and minor calcite, talc, serpentine, sphene and apatite. The practice proves that this method is a feasible technology for the identification of the altered mineral assemblage of kimberlite.