A suction assembly includes a main body, a sealing ring, an air duct, and a suction head. The main body includes a columnar wall, a top cover arranged at one end of the columnar wall and defining a first through hole, and a bottom cover arranged at another end of the columnar wall and defining a second through hole. The first through hole communicates with a negative pressure generating device. The sealing ring is sealed in the main body and movably arranged between the top cover and the bottom cover. The air duct includes a first end and a second end opposite the first end. The first end passes through the second through hole and is fixed in the sealing ring. The suction head is coupled to the second end.