Diamond magnetic susceptibility measurement is to measure the magnetization of the diamond sample. Diamond is composed of carbon atoms, pure diamond should not sense the magnetic, since the diamond used for the synthesis of metal as catalyst, a synthetic diamond interior containing various amounts of metal impurities, especially the inclusion within the crystal resulting diamond has a magnetism, and therefore , synthetic diamond magnetic size, not only its internal impurities and inclusions content component has a direct relationship, but also with its physical and chemical properties and quality indicators (such as toughness, strength, specific gravity, thermal stability, color, transparency, etc.) there is a close relationship. By measuring the magnetic susceptibility of this simple way of non-destructive testing, characterization of the nature of the impurities in synthetic diamond, toughness, strength, thermal stability, etc., has important practical value. Generally the lower the susceptibility of the diamond, the less impurities in diamond, the toughness better, better transparency, and wear properties of diamond tools is better. Some large foreign companies have internal susceptibility tests as an indicator to control the quality of diamond.