Abstract: Abstract: Kitchen waste easily sours and smells during the process of collection and transportation because of its high content of water and organic substrate, which hinders its resource utilization. Therefore, how to solve the problem of kitchen waste bacteriostatic preservation is the key to achieve the resource utilization of kitchen waste. The final purpose of anaerobic digestion is to produce methane, so we want to find an effective pretreatment method which can not only realize the kitchen waste bacteriostatic preservation, but also promote the methane production. In this study, fresh kitchen waste was inoculated with yeast and acetic acid bacteria to conduct ethanol and acetic acid pre-fermentation respectively. Ethanol and acetic acid pre-fermentation groups were compared to the control group, which group's kitchen waste had no inoculation and just was placed in anaerobic environment. After pre-fermentation, the pretreated kitchen waste was mixed with distillers' grains to anaerobic methane fermentation. All groups underwent anaerobic methane fermentation under the same experimental condition. The study was aimed to make clear of the effect of the 2 pre-fermentation methods on acidification bacteriostasis and anaerobic co-digestion compared to the control group by investigating the methane yield, the changes of parameters such as pH value, VFAs (volatile fatty acids), acetic acid, propanoic acid and ethanol mass concentration during hydrolytic acidification and methane fermentation phase. The results showed that ethanol and acetic acid pre-fermentation performed well on acidification bacteriostasis, as the numbers of Escherichia coli and Staphylococcus aureus both decreased by 2 orders of magnitude during pre-fermentation phase through plate counting method. The descending order for the accumulated methane yield was: ethanol pre-fermentation group (4725 mL) > control group (3896 mL) > acetic acid pre-fermentation group (3135 mL), and the accumulated methane yield of ethanol pre-fermentation group was 21.3% and 49.8% higher than control group and acetic acid pre-fermentation group, respectively. Through the above results we found that ethanol pre-fermentation group could not only realize the kitchen waste bacteriostatic preservation, but also promote the methane production. Ethanol pre-fermentation group was found to have the highest ethanol mass concentration and pH value while the lowest VFAs, acetic acid and propionate acid mass concentration in both hydrolytic acidification and methane fermentation phase. Through ethanol pre-fermentation process, kitchen waste was converted into ethanol, which decreased the VFAs' concentration in the meantime. As is well known, the accumulation of VFAs leads to the activity of methanogens decreasing, which results in the reduction of gas production rate. Meanwhile, methanogens' activity is very sensitive to tiny changes of propanoic acid concentration. Since ethanol is neutral, which will not led to the pH value decreasing, and it can be converted into acetic acid gradually, which can be directly used by methanogens, this ethanol pre-fermentation process can indeed improve digestion efficiency and methane yield in the following anaerobic system. Moreover, with less VFAs produced at the beginning of digestion, the acid accumulation issue can be well relieved in the later stage. In conclusion, ethanol pre-fermentation is an effective treatment which can do well in the acidification bacteriostasis of kitchen waste and also stabilize the fermentation system to improve methane production rate.