The large-scale connection of electric vehicles and photovoltaic power generation system to the distribution network increases the single-phase power supply and load, which aggravates the single-phase operation problem. In order to ensure the power supply quality of the power grid, a large number of adjustable single-phase and three-phase compensation regulation devices are used in the power grid, so the optimal power flow of three-phase unbalanced distribution network is studied. The optimal power flow of distribution network under the condition of three-phase unbalance is solved and analyzed, and the optimal power flow model of multi-period distribution network is established with the optimization objective of minimizing the active power loss. The non-convex nonlinear optimal power flow model is transformed into a linear model by second-order cone programming, which reduces the difficulty of solving and improves the efficiency of solving without loss of accuracy. Pyomo modeling tool and Gurobi algorithm package are used to solve the model, and the power flow error is analyzed, which verifies the feasibility and effectiveness of the method.