As a major element in the earth, Magnesium (Mg) takes par t in all geochemical processes. It is also a component part of the 26Al-26Mg chronology for meteorites. The development of the high-precision Mg isotopic measurement technique using multiple-collector inductively coupled mass spectrometry (MC_ICP_MS) makes it possible for Mg isotopes to act as a research tool in geochemistry, cosmochemistry and medicine. Mg isotope studies can be used in such research fields as relative ages of inclusions in meteorite s, reconstruction of palaeo-envirment and intestinal Mg absorption