With the continuous access of distributed generations(DGs) in distribution network, a power flow calculation method for three-phase unbalance distribution network is proposed in order to adapt to the access trend of DGs. Firstly, considering the demand that a lot of DGs will be accessed into distribution network, the influence of power flow distribution in the whole network with DGs is analyzed, and the three-phase power flow calculation model in the unbalance distribution network is established. Then, based on the established power flow calculation model, Newton-Raphson iterative method is used to solve the issue, as well as the analysis of node admittance matrix and Jacobi matrix in three-phase unbalanced distribution network is provided. At last, the correctness and validity of the proposed power flow calculation method are verified by the example analysis in the simulation system.