Submerged membrane bio-reactor （SMBR）is a high-efficiency wastewater treatment technology that combines membrane separation technology with traditional biological treatment technology. The effect that regularity of aeration intensity and aeration pore sizes on fluid mechanics characteristics of hollow fiber membrane surface was analyzed based on the PIV fluorescent particle technology. The bubbles movement of flow field near membrane surface in the aeration pore was studied when its size was 1.5mm by using Size—Shape—Analysis modular, and the changing rule of Reynolds stress on the surface of membrane under seven aeration intensities of 24L/h, 48L/h, 72L/h, 96L/h, 140L/h, 180L/h and 220L/h was investigated. The results indicated that the bubble shape was oval and its equivalent diameter was concentrated in 5～6mm when bubble aeration was exercised by the 1.5mm aperture with velocities on the bubble were 0.1～0.2m/s. Aeration intensity was positively correlated with Reynolds stress. Aeration pore size of 1.5mm and aeration intensity of 140L/h was considered as the best aeration pore size and aeration intensity values, because it can provide a greater Reynolds stress. This subject laid a theoretical foundation for the optimization of flow field in membrane bioreactor so as to improve the membrane fouling problem.