The metal additive manufacturing technology has the intrinsic characteristics of "micro-area super-metallurgy" and "rapid cooling solidification . Realizing the dynamic monitoring and control of the evolution of defects, stress and organization in the additive manufacturing process is currently the difficulty and hotspot of the international frontier research in this field. In this paper, starting from the key common problems of metal additive manufacturing in the fields of aeronautical space and automobile, the research progress of metal additive manufacturing, based on two methods of synchrotron radiation and neutron diffraction, showed in the following aspects: metallurgical dynamics in metal additive manufacturing and in-situ analysis of its internal defects, superconventional solidification of liquid metal, microstructure and phase transition process, formation and evolution of internal stress. Subsequently, the deficiencies of the research progress were explained, and the future development of metal additive manufacturing was prospected.