The purposes of this study were to investigate the effect of waste leachate (WL) addition on batch anaerobic digestion of food waste (FW), and to examine the influence of mixture ratio on the co-digestion process. The results showed that anaerobic digestion of FW was greatly enhanced by WL addition, as indicated by the higher methane yield, higher methane content, more volatile solids (VS) destruction, and higher stability. Although WL was rich in volatile fatty acids (VFA), its addition did not cause VFA inhibition. It was found that WL addition was beneficial to accelerate the start-up and shorten the long reaction time of the batch anaerobic process. The time to reach the peak methane yield was reduced by 1, 2, and 4 days with WL addition. The optimum FW to WL ratio was 77.9:22.1 with the highest methane yield (416 mL/g VS), the highest methane content (64.3%), the greatest VS removal (77.6%), and stable performance. These results confirmed the positive effects of WL addition on methane fermentation from FW.