The invention discloses an acid liquor removing device and method for kerogen preparation. The device comprises the following equipment: a reaction tank, a suction head, a liquid storage tank, a buffer bottle, a vacuum pump, a first connecting pipe, a second connecting pipe and a third connecting pipe. The method comprises the following steps: connecting equipment of the device, closing a discharge port valve of the liquid storage tank, and setting initial vacuum negative pressure; enabling the suction head to be in contact with the liquid level of the acid liquor, and removing the acid liquor; and when the liquid level of the acid liquid entering the liquid storage tank is close to the bottom end of the outlet connecting pipe of the liquid storage tank, the acid liquid in the liquid storage tank is discharged. And repeating the steps until the target acid liquor in the reaction tank is completely removed. The vacuum pump is used for replacing a traditional water pumping pipe, water resources are saved to a great extent, meanwhile, the suction force of the device is adjustable, the operation process is more accurate and stable, the waste liquid treatment cost is saved, and the enterprise economic expenditure is reduced.