This paper introduces a novel backward/forward sweep algorithm for both fundamental and harmonics flow calculation in distribution network. In this algorithm, the fundamental and harmonic currents of each branch are calculated by equivalent current injection method. The relationship between branch currents and harmonic currents of each order on a radial feeder can be calculated by summing the injection current from the receiving end toward the sending end of the feeder. After obtaining the branch currents, both the harmonics bus voltage and the fundamental bus voltage can be easily obtained from the sending end to the receiving end based on the Kirchhoff's Voltage Law. By using this method, the LU decomposition is avoided and it will save huge computational time. Base on special hierarchy characteristic of radial network, the branches are sorted by layers. So that the branch power loss and voltage drop can be computed in parallel at each level. The computational time can be further reduced. The test results demonstrate the flexible, accuracy and efficiency of the proposed method.