The distribution transformer plays a key role in distribution network. It undertakes the task of the voltage transformation, energy distribution. But a lot of loss of the transformer in operation has affected the economy of the distribution network. Therefore in order to save energy, it is essential to consider the transformer economical operation mode during distribution network load distribution. Combining with the comprehensive power loss curve and critical load of transformer in parallel, the interval of economic operation of transformers in different operation modes is deduced in this paper. Then the unavailability of transformers in different operation mode is calculated. The distribution network load distribution model is proposed which takes distribution network reliability, the economy of parallel transformers and load balancing as the object function. The topological structure, load capacity and operating limits are given as the restriction conditions. Using optimization algorithm to analyze the model, the appropriate transformer operation mode and the load distribution scheme can be determined. Whats more, a simple double power distribution network is used to show the steps of the distribution network load distribution considering the transformer economic operation mode. It makes clear that the model can determine the transformer operation mode and the load distribution strategy. The optimization results contribute to improving the distribution network reliability and economy.