The utility model relates to a membrane biological reaction aeration subassembly. A membrane biological reaction aeration subassembly includes: carry trachea and aeration main pipe, aeration main pipehas the inlet end, and the inlet end communicates with carrying the trachea, aeration main pipe is last to have seted up a plurality of aeration holes, and the aeration hole includes first aeration hole and second aeration hole, and the aperture in first aeration hole is greater than the aperture in second aeration hole, on aeration main pipe's extending direction, first aeration hole separates with second aeration hole each other arranges in turn. Above -mentioned membrane biological reaction aeration subassembly makes adjacent two the inhomogeneous aerations of pore forming that expose to the sun, and when having the dirt to get into in the aeration hole, the dirt is discharged from first aeration hole, has prevented that the aeration hole from being blockked up, and separates first aeration hole each other with second aeration hole and arrange in turn, has guaranteed the homogeneity of aeration main pipe whole aeration, also is favorable to preventing aeration main pipe's jam.