Abstract:In this paper, according to the structure and physical field of the earth, and considering the nature of the hydrogen deduced by its position in periodic table of elements and its electronic distributions and combining the developments of modern codensed states and structural chemistry with ultra-high pressure technique, it is shown that under physical chemistry environments of lower mantle-core, hydrogen encounters about 10~8atm. ultra-high pressure and possesses sufficient potential difference of thermodynamics. Therefore, the hydrogen may be condensed to be metal hydrogen which can principally be regarded as self-excited generator. It reveals the origins of magnetic, gravitational and electric fields of the earth.