Abstract: To optimize the initial acidogenic conditions of pig manure mixture with straws, effects of different sludge (activated and digestion sludge) and carbon nitrogen ratios (11.9、16.0、17.8 and 22.2) on solid acidogenic process at initial start were investigated to obtain a better inoculum and suitable ratio of pig manure and crop straws. The results showed that activated sludge had higher abilities of degradation and acid production. When carbon nitrogen ratio was adjusted to 17.8 and the mixture was inoculated with activated sludge, volatile acid concentration and VS degradation were elevated to 14 g/L and 23%, whereas acetic and propionic acid contents in volatile acid were stabled at 50% and 20%, respectively. The results demonstrated a favorable hydrolytic and acidogenic performance was occurred, which can meet the requirement of acidogenic process at initial start.