Firstlythe calculation methods of freight trains at the flat slope and variable slope points are analyzed. Aiming at reducing the traction energy consumption of freight trainsan energy-saving optimization model of freight trains is established with time and speed limit as constraints. Considering the existence of temporary speed limit in the linean energy-saving strategy based on different interval division is proposedwhich divides the interval according to the working condition sequence under the fastest speed curveinserts the idling working condition into the interval to form the energy-saving condition sequenceand use the improved whale optimization algorithm to solve the position of the condition conversion point in each interval. Finallythe effectiveness of the proposed energy-saving strategy is verified by comparing it with the classical four stage energy-saving strategy in simulation and actual lines.