In order to achieve efficient, fair and transparent distribution of power distribution network, a distribution network power transaction method based on block chain is proposed. The technical characteristics of block chain are introduced. The block chain structure of power distribution in distribution network is put forward in view of the difficulties of current power distribution network containing new energy. This paper introduces the concrete steps and transaction process of power distribution network based on block chain and studies the main content of the block chain based on the XML organization. The domestic security algorithms, SM2 and SM3 are introduced into block chain applications. Finally, the situation of power transaction in distribution network based on block chain is designed. The results prove the effectiveness of the power transaction method based on block chain in distribution network. This work is supported by National Natural Science Foundation of China (No. 51807116).