Distributed generation connection leads to the new kinds of nodes appeared in distribution network. Thus, it makes the traditional calculation method of back/forward sweep power flow fail. Based on the static characteristics of load voltage of constant power, constant current and constant resistance, this paper proposes an improved forward-backward sweep method for power flow calculation of different kinds of node types of distributed generation. The method focuses on the wind power, photovoltaic cells, fuel cell and gas turbine, establishes the mathematical modeling respectively, when dealing with the PV node, it uses reactive power compensation device for power correction, and the reactive power allocation principle to determine the initial value. In addition, according to the radial distribution characteristics, with the method of searching the leaf node, it forms a convenient parameter matrix which is convenient for forward-backword sweep method. The IEEE33 distribution system shows that the proposed method convergence performance is strong, and can effectively solve the problem of power flow calculation containing different distributed generation.