Abstract: The characteristics of kimberlites, their mantle xenoliths and diamonds are briefly introduced in this paper. Very close petrogenesis relationship between them has been recognized. Kimberlites are rare igneous rock types discovering in the earth and the kimberlitic magmas derived from mantle at 200km depth. Diamonds are crystallized and stabilized at high pressure, high temperature and low oxygen fugacity condition in the mantle. When the kimberlitic magmas rapid ascend they can carry mantle rocks and their segregated minerals such as olivines, garnets, pyroxenes, spinals etc. to uplift from mantle to upper crust or surface. A very important event is the diamonds also as xenocrystals born by magma and preserved in kimberlites. Except the solid diffuse of carbon particles, melts and fluids are the non-neglected factors at the formed processes of diamonds.

Key words: kimberlite, diamond, mantle xenolith, oxygen fugacity