A door lock with an energy-saving device, comprising: an electromagnet assembly secured on the door frame, which has an electromagnet and a control circuit board, and an adsorption assembly secured on the door board, which has a positioning unit and an iron plate, a set of linkage sensing mechanism set on the electromagnet, and a set of clutch mechanism set on the adsorption assembly; Thereby, when close the door board into the door frame, the control circuit board supplies power to the electromagnet with the high current in the normal locking mode to attract iron plate, and then, the clutch mechanism drives the linkage sensing mechanism to act, triggering the control circuit board to supply power with low current in the power-saving lock mode to maintain the closed state of the door panel.