For solving diseconomy problems in distribution transformers reconstruction, simple and practical criterions based on the actual situation are developed to judge the various parameters of distribution transformers. The distribution transformers selected without construction risks are divided into three parts and they considered to be reconstructed for energy saving, such as replacing for new energy-saving distribution transformers, and increasing the capacity for high-load rate transformers. For each part of the distribution transformers, the reconstruction scheme under constraints with the least ratio of investment and efficiency is optimal. The overall optimal scheme is composed of each optimal scheme. A certain line in Chongqing area is taken as example. Distribution transformer reconstruction schemes are developed using the method. The computed result shows that the method can reduce line losses effectively, while increasing operation level of equipment.