The invention relates to a process for enhancing denitrogenation of a 
membrane bioreactor by anaerobic 
fermentation acid production. The process adopts an enhanced anaerobic tank, an anoxic tank and an aerobic tank. After entering the process, the 
sewage undergoes biochemical treatments including anaerobic 
fermentation, anaerobic 
denitrification and aerobic 
nitrification under the action of different kinds of microorganisms, and finally the 
effluent is sucked and collected by membrane 
filtration. By optimizing the growth environment of microorganisms in the anaerobic section, the process, on the one hand, promotes 
hydrolysis acidification of particle-stage organic matters (including 
colloid-state organic matters), slowly-degradable organic matters and hardly-degradable organic matters in the raw 
sewage, and on the other hand, produces acids from the excessive 
activated sludge which is discharged to the anaerobic tank to provide high-quality carbon sources for anaerobic 
denitrification. Besides, the process enhances the biological 
denitrification process by increasing 
sludge concentration, solves the problem of insufficient 
carbon source in biological 
denitrification process, and achieves the purpose of removing 
total nitrogen from the 
sewage with high efficiency by virtue of high-efficiency 
cut-off and separation characteristics of the membrane. The process can supplement carbon sources to the denitrification section for enhanced denitrogenation by fully utilizing converted carbon sources in the incoming water and carbon sources generated by 
sludge fermentation in the process without needing extra carbon sources. The process is simple and flexible in control, and the 
total nitrogen in the 
effluent can reach or exceed the first-class (A-class) 
discharge standard.