Deterioration of anaerobic fermentation can occur with the presence of grease in food waste, but little information on eliminating this deterioration is currently available. In this study, it was found that the presence of 10 g/L grease decreased SCFAs production from 16.97 to 13.32 g COD/L and prolonged the optimal fermentation time to 7 days, but could be respectively recovered to 39.10 g COD/L and 4 days with 0.02 mg/g VS (volatile solids) calcium peroxide addition. Mechanism investigations indicated that calcium peroxide facilitated biodegradable organics release and improved grease degradation, thereby providing enough nutrients and better growth environments to microbes for SCFAs-producing, which could be further supported by the elevated enzymes activities responding to hydrolysis and acidification process. Further investigations revealed that among the main derivates of calcium peroxide, OH- and Ca2+ played vital role in SCFAs production promotion, O2- and OH radicals were the main contributors to grease degradation.