The access of distributed generations (DGs) leads to the loss allocation problems of distribution network (DN) becoming more complicated. When the marginal loss coefficients (MLC) method based on the proportional coefficients is applied in DN with DGs, the allocation gap between market members is too large, leading to lack of rationality. Firstly, the absolute value of the positive and negative network loss allocation calculated by the proportional method are summed. And then, based on this sum, the network loss allocation of each load bus are recalculated. Secondly, considering the equality constraints between the total loss allocation and the actual total loss, the reward and punishment coefficients are used to increase the positive network loss allocations and reduce the negative network loss allocations. The reward and punishment coefficients are obtained by solving the constructed equations and applied to correct the initial network loss allocations. The improved method can avoid the offset of positive and negative allocation, reduce the allocation gap of members, and reasonably allocate the loss in DN. The results which are obtained by IEEE 33-bus system show that the proposed method can be used as a reference for loss allocation of DN with DGs.