The invention relates to the technical field of engines, and discloses an engine variable displacement control method and device and an engine. The engine variable displacement control method comprises the steps that one air cylinder in a plurality of air cylinders of the engine can be switched between a dynamic cylinder stopping mode and a full working mode where repeated circular work doing is conducted; and in the dynamic cylinder stopping mode, the air cylinder of which the working mode is switched continuously and circularly does work, and the number of times of circular work doing is smaller than the number of times of circular work doing in the full working mode. According to the engine variable displacement control method, dynamic cylinder stopping can be conducted on the air cylinders of the engine, so that power output of the engine is more uniform; and meanwhile, the air cylinder abrasion uniformity can be remarkably improved, and vibration and noise produced during cylinder stopping of the engine are reduced.