Abstract: Iron loss and copper loss are basic losses that affect the efficiency of distribution transformers,especially the occurrence of three-phase load unbalance can also bring additional losses. In order to maximize the efficiency of distribution transformers, combined with the current unbalanced situations of three-phase amplitude and power factors in low-voltage power supply and distribution systems,theoretical analysis is conducted on the factors affecting the efficiency of distribution transformers through mathematical modeling. The measurement formula for the relationship between three-phase load unbalance and distribution transformer efficiency is established, and an algorithm based on joint mechanism for maximizing distribution transformer efficiency is proposed. The proposed theory is verified and analyzed through numerical examples and experimental methods, and the results show that the efficiency of distribution transformers can be effectively improved by controlling the neutral line current. Based on the experimental results, improvement measures have been proposed to maximize the efficiency of distribution transformers