The wastewater effluent quality in BNR systems critically depends on the availability of readily biodegradable carbon source in the influent. Primary sludge in WWTPs is identified as a renewable resource for internal carbon source production. The effects of SRT, temperature and RR on the anaerobic fermentation process performance were assessed and the biological nutrient removal performance was evaluated in this study. The results showed SRT of 5d, temperature of 30ºC and RR of 20 is the optimal operating condition for primary sludge anaerobic fermentation. Under the optimal operating condition, the SCOD and VFA production rate of the fermentation product is in the range of 0.39~0.48 mg SCOD/mg VSS and 0.25~0.31 mgVFA/mg VSS. The full-scale application of internal carbon source production has achieved better effluent quality (TN 7.1 mg/L and TP 0.3 mg/L) compared to the effluent (TN 18.4 mg/L and TP 1.3 mg/L) without adding carbon source. Primary sludge fermentation can be considered as an appropriate solution for carbon source production and contribute to the goal of meeting stringent wastewater discharge standard.