The invention discloses a stirring assembly applied to a sewage stirring tank. The stirring assembly comprises a transmission shaft and a stirring plate; a cavity is formed in the transmission shaft,and placement grooves are formed in two sides of an outer wall of the transmission shaft; an air bag that can swell by inflation is arranged in each placement groove, a connecting pipe is arranged between the each bag and the cavity, and the cavity and the air bags are communicated by means of the connecting pipes; a connecting hole is formed in the stirring plate, and the transmission shaft penetrates in the connecting hole; accommodating cavities, each having a circular cross section are formed in two sides of an inner wall of the connecting hole, each accommodating cavity is communicated with the connecting hole, and the diameter of each accommodating cavity is gradually increased towards a direction away from the accommodating cavity; after the air bags are inflated, the air bags can fill the accommodating cavities; the stirring plate is fixed on the transmission shaft, a limit ring is further arranged on the transmission shaft, and the limit ring is located above the stirring plate; when the air bags fill the accommodating cavities, the bottom of the limit ring is in contact with the top of the stirring plate; several sewage discharge holes are further formed in the stirring plate, and the sewage discharge holes are communicated with the accommodating cavities.