Intentional islanding operation of distribution networks with multi?source is an important measure to ensure the power supply of critical loads and improve the safety and reliability of the distribution system when a large?scale grid fails under extreme conditions. Therefore, according to the distribution of different types of distributed power supply and important load, with the goal of minimum path weight and maximum recovery of important load, the optimization model of the distribution network island black start scheme at the early stage of major power failure is established to ensure the recovery of critical load in the shortest possible time. The advantages of fast convergence speed and high calculation accuracy of the BFGS trust region algorithm are fully used to propose a dynamic power flow analysis method for a self?organizing restoration process in intentional islanded distribution networks with multi?source. Then, the dynamic power flow's frequency and node voltage results are used to judge the feasibility of the black start scheme. The improved IEEE 33?node power distribution system is taken as a simulation example to verify the effectiveness and innovation of the proposed method.