A line loss prediction method based on power exchange and truncated total least square method is proposed, which is of great significance for guiding the power allocation of transmission network among multiple regions. Firstly, a line loss prediction model combined with power exchange is constructed, and the power exchange prediction value is calculated according to the location of each bidding area, transmission capacity of interconnection lines between regions and the specific electricity price. Secondly, considering the power demand, supply and the total level of wind power in each region, as well as the power exchange with adjacent regions, a line loss prediction algorithm based on the truncated total least square (TTLS) method is presented. Finally, the effectiveness of the proposed method is verified by the open data set and the collected measured data set.