Aiming at radial distribution network topology features，an advanced forward and backward sweep algorithm is proposed based on the traditional one． Using the characteristics of non-leaf node acted as an end node of the branch，we determine the power and voltage calculation order before power flow calculation by searching leaf nodes and new leaf nodes repeatedly． Nodes can be numbered randomly and branches need no layering． The calcu-lation process is simple and intuitive which could be applied in any radial distribution network flow calculation． A-nalysising the calculation of the example by MATLAB，the result shows that the proposed method is feasible and ef-fective．