The supercooling and crystallization of water are affected by many factors，the investigation of which is of great significance in the field of food frozen and conservation and low temperature preservation of biology.Experiments were carried out to investigate the supercooling and crystallization of water under DC magnetic fields with different intensity.The results show that the DC magnetic field can reduce the lowest unfrozen temperature and increase supercooling.The time that water remains supercooled increases with the increase of intensity of DC magnetic filed.The crystallization speed also increases obviously.This effect is considered to relate to the formation of water molecular hydrogen bonds.