Acidogenic fermentation with food waste and using the fermentation products as carbon sources for nitrogen removal were investigated in this study. It was found that, related to the shifts of microbial communities, a two-stage organic transformation processes (carbohydrate→lactate→VFAs) existed during the fermentation period. After 72h, the relative abundance of Lactobacillus achieved to 99.3% accompanying with the maximal lactate (45.2g/L). Using the fermentation products at different stages (before fermentation, partial fermentation, lactate and VFAs) as external carbon sources for denitrification, it was found that, similar to the sodium acetate, the products mainly containing lactate showed high denitrification potential (0.15g NO₃^--N/g COD) and rate [6.1g NO₃^--N/(g VSS·h)] with high organics utilization efficiency and low heterotrophic yield and could achieve complete denitrification at C/N over 5.7. Applying the fermentation producsts as external carbon sources in a SBR could obviously improve nitrogen removal efficiencies and showed no negative effects on nitrification. So lactic acid fermentation with food waste could not only shorten the fermentation period, decrease the cost of waste dispose, but also obtain high-quality carbon sources for denitrification.