The invention discloses a method for producing a wastewater denitrification carbon source through lactic acid fermentation of kitchen waste, and belongs to the technical field of solid waste resourceful treatment. The method comprises the steps of adopting kitchen waste as a raw material; sorting and impurity removal, controlling the solid-to-liquid ratio, grinding, pulping, and carrying out quality-based and phase-splitting treatment; after the waste oil is heated and recycled, the residual garbage slurry is injected into an anaerobic fermentation tank for batch lactic acid fermentation, after fermentation is finished, solid-liquid separation is carried out, lactic acid-containing supernatant can be directly used as a liquid carbon source in the sewage denitrification stage, a good biological denitrification effect is achieved, nitrogen-containing residues can be collected and recycled, and full recycling is achieved. According to the invention, kitchen waste is directly used for efficient open lactic acid fermentation; according to the method, the indigenous microbial flora in the kitchen waste is fully utilized to hydrolyze the substrate and efficiently and directionally convertthe substrate into lactic acid, exogenous nutrition and industrial enzyme preparations do not need to be added, the process is simple, the production cost is low, a cheap carbon source is provided for a denitrification section of a sewage treatment plant while resource utilization of the kitchen waste is realized, and the biological denitrification efficiency is improved.