In the manual adjustment of the three-phase unbalanced load in distribution network, those factors, such as the fluctuation of the instantaneous detection current, and so on, would decrease the adjustment effect significantly. To address this problem, a method is proposed to adjust the unbalanced three-phase load in the distribution network based on its historical power data and each customer’s power consumption in this paper. In addition, the problems of customer reduction and new customer accessing are illustrated and the model updating method is elaborated. Finally, the model is tested by a certain distribution network historical samples data, and it is proved that the unbalance degree of the three-phase load of distribution station could be decreased significantly. This work is supported by National Natural Science Foundation of China (No.51577051) and Science and Technology Project of State Grid Corporation of China (No. SGJS0000YXJS1501044).