The invention discloses a method and 
system for medium-and-long-term power transaction curve 
decomposition. The method comprises the following steps: S1, acquiring power 
consumer data, power medium and long term transaction contract data and a spot market predicted price curve; S2, according to the power 
consumer data, establishing a load prediction curve of the power seller in combination with the electric quantity in the power medium-and-long-term transaction contract data; S3, establishing a comprehensive price curve of medium-and-long-term power transaction according to the medium-and-long-term power transaction contract data; S4, establishing an 
electric power medium and long term transaction curve 
decomposition model according to the spot 
market prediction price curve, the load prediction curve of the 
electricity seller and the comprehensive price curve of the 
electric power medium and long term transaction; and S5, obtaining an optimized power seller load 
decomposition curve according to the power medium-and-long-term transaction curve decomposition model. The load decomposition curve of the 
electricity seller obtained by using the medium-and-long-term 
electric power transaction curve decomposition method can increase the income of an 
electricity selling company in the electric power transaction.