Abstract：Distributed generation (DG) access to the distribution network changes the power flow characteristics of the system, which will have a certain impact on the network loss and steady-state voltage of the distribution network. Firstly, the paper establishes the mathematical model of photovoltaic power grid integration, and concludes that there are two types of nodes in the distribution network with photovoltaic power supply, PI node and PV node, and gives the models of these two nodes in power flow calculation. Secondly, the improved forward and backward power flow algorithm is used to calculate the distribution network power flow with photovoltaic power supply. When dealing with PV nodes, the compensation current is injected into the node, so that the PV nodes can be converted to PQ nodes. Finally, the simulation results in the distribution network with 14 nodes of IEEE show that the proposed algorithm is feasible.