The research on distributed generation technology meets the great demand of China. Focusing on the vital theory of the complicated dynamic performance and the safe and efficient operation of high penetration micro-grid， four fundamental problems in the study of distributed generation system are proposed systematically， including the property of micro-grid and the principle of interaction of high penetration micro-grid with the bulk power system; the planning theory and method of new distribution system containing micro-grids; the protection and control of micro-grid and distribution system with micro-grids; and the integrated simulation of distributed generation system and the optimization method of energy management. The research directions of each scientific problems are surveyed and anticipated.