Abstract: ρ(VFA) is a key factor in enhanced biological phosphorus removal process,and the effect of biological phosphorous removal can be improved with VFA increased in influent.The effects of primary sludge fermentation on thep (VFA)、ρ(C):ρ(P) in the biochemistry reaction system are discussed by comparing the results of pilot test and full scale plant.The results showed that primary fermentation can increase influent index such asρ(BOD₅),ρ(CODcr),ρ(TP),ρ(SP),ρ(SS) comparing the effluent from full scale plant primary sedimentation,separately increased,61.1%、36.5 %、36.1%、17.36 %和52.0 %,also the biologic catabolism index improve 20.40 %,and the technology especially in favor of the influent VFA,increased from 12 to 56,about3.7 times,enhance biological phosphorus and nitrogen removal to the biological system.The technology of sludge fermentation can be applied to the municipal wastewater treatment plant where the quantity of the carbon source is low and difficult to biological phosphorus and nitrogen removal in high efficiency.