Most of the traditional line loss calculation methods are based on a period of time for line loss calculation, that is, the load current, voltage and other factors are calculated in an average manner over a period of time. In the selection of period, since the variation characteristics of the load itself are not taken into consideration, it lacks scientific basis. In this paper, the time-oriented process method is used to describe the change of load, and using hybrid clustering to divide time period, so the irregular load is divided into linear regular load. Finally, the line loss calculation is performed for each time period, which increases the theoretical accuracy of the line loss calculation and reduces the number of calculation.