Because of the existence of asymmetrical parameters and unbalanced loads，a power system may operate in an unbalanced state even if there is no fault in the system.A new three-phase power-flow method for asymmetrical power systems power flow calculation is presented.This method uses a hybrid approach with symmetrical components and phase components to model the system，and solves the power flow through decomposition and coordination algorithms.The algorithm proposed combines the flexibility of phase component method and the efficiency of symmetrical component method.It is suitable for power flow and fault calculation of transmission systems as well as high/medium voltage distribution systems.Three IEEE standard systems with different size and a real system are used for case study.Test results show that the method proposed has high accuracy and convergence，and has low sensitivity to the system unbalance.