In this study, food waste and maize straw were used as feedstock, and the two-phase high-solid anaerobic digestion (TP-HSAD) technology was used to optimize the process parameters of leachate reflux in acid-production stage. Results indicated that compared with other waste activated sludge, pig manure digestate (PM) as leachate can achieve better hydrolysis and acidification effect. The increase of leachate reflux ratio can shorten the fermentation time of the acid-producing stage and increase the fermentation efficiency. When the reflux ratio was 32:1, peak concentration of volatile fatty acids (VFAs) was 45.4 g/L and the volatile solids (VS) removal rate was 61.7%. Reflux frequency has minimal effect on the concentration of VFAs and the degree of degradation of VS, but a higher reflux frequency will prolong the reaction time of acid-production stage. When PM is used as reflux leachate, the HSAD reactor can improve the hydrolysis and acidification of the anaerobic fermentation.