Abstract: The distribution network loss apportionment method does not consider the influence of unbalanced load on the apportionment of line loss in the three-phase three-wire distribution network, but the three-phase unbalance will lead to unreasonable apportionment of network loss in the three-phase three-wire distribution network. Therefore, it is necessary to propose a three-phase three-wire distribution network loss apportionment method that considers the influence of three-phase unbalance. By analyzing the most commonly used improved average network loss apportionment method at this stage, the network loss apportionment of each node of the distribution network is unreasonable under the condition of three-phase imbalance in the distribution network, and a distribution network loss apportionment method considering the influence of unbalanced load is proposed. This method divides the network loss of distribution network with unbalanced load into two parts, positive sequence network loss and negative sequence network loss. The positive-sequence network loss is apportioned to each node using the average network loss coefficient method, while the negative-sequence network loss is apportioned to each node according to the proposed negative-sequence network loss allocation factor, and the total network loss apportioned to each node is obtained. By adding three-phase unbalanced loads to the IEEE 9-node distribution system and comparing and analyzing the improved average network loss sharing method and the new network loss sharing method proposed, the network loss sharing value of unbalanced loads calculated by using the proposed method is 38.94% larger than that calculated by the traditional method. And as the degree of load imbalance increases, the network loss value for unbalanced load allocation also increases, and its punishment is also greater, proving that the network loss allocation method is more reasonable.