A heat treatment device for a PET bottle preform with an integral handle includes an air-cooling knife, a heating furnace, and a transport mechanism. The air-cooling knife is disposed on an outlet side of the heating furnace, the bottle preform is transported into the heating furnace through the transport mechanism, heated in the heating furnace, and transported to the air-cooling knife, and the air-cooling knife jets airflow to and cools a lower end of a handle of the bottle preform, appropriately reducing the temperature at junction of the lower end of the handle and a bottle body so that a gentle transition between the temperature of the bottle body and the temperature of the handle is achieved, and the handle is not easily deformed after the bottle preform is blown, thereby effectively improving the quality of the bottle preform after blown.