Abstract: Abstract: As a way of resource utilization of livestock farming wastewater, the production of volatile fatty acids (VFAs) from swine wastewater by anaerobic fermentation has attracted more and more attention. But the production process of VFAs from swine wastewater by anaerobic fermentation anaerobic is necessary to be studied in depth. Temperature is one of the important parameters in the VFAs production process. In order to understand the VFAs production process of swine wastewater thoroughly, the effect of fermentation temperature on the yield of VFAs from swine wastewater were studied in an anaerobic sequencing batch reactors heated in a thermostat water bath at the temperature of 25, 30, 35 and 40 ℃, respectively. The anaerobic fermentation slurry was sampled hourly within 12 h and the samples were taken once a day. The concentration of VFAs was then measured with chemical titration method. The results exhibit that the fermentation temperature affects the VFAs concentration of the system. The concentration of VFAs in the swine wastewater system under mesophilic anaerobic conditions became stable in 8 h. The maximum concentration of VFAs decreased, but the time for VFAs to reach stable became shorter when the fermentation temperature increased from 25 to 40 ℃. It meant that the lower fermentation temperature was favourable to yield VFAs, but higher fermentation temperature shortened the span of VFAs production process. The 16rsDNA high-throughput sequencing technology was used to study the changes of bacterial community structure in acclimated inoculated sludge in the anaerobic system at different fermentation temperatures. It was found that the Actinobacteria, Proteobacteria, Synergistia and methanogens (including Methanobacteria and Methanomicrobia) which were common microbial communities could be found in anaerobic environment and Clostridia is the dominant bacterium followed by Bacteroidia in all acclimated inoculated sludge samples at different temperatures. The relative abundance of the mixed microbial culture significantly changed at different temperature and it reflected a significant shift in microbial community structure. When the acclimation temperature of anaerobic sludge increased from 25 to 40 ℃, the abundance of Bacteroidia decreased, while the abundance of Clostridia, Bacilli and Synergistia increased. The different suitable living environmental temperature for each bacteria could explain the change of the microbial community abundance in the acclimated inoculated sludge. When the temperature was 25 ℃, it was suitable for Bacteroidia to grow and reproduce, which could use carbohydrates in the system and produce small molecule acids quickly. The temperature was unfavorable to the survival of Synergistia. The VFAs accumulation occured under the combined effect of acidify bacteria and fatty acid-utilizing bacteria. When the temperate increasing, the number of cellulose-degrading bacteria increased, and the hydrolysis rate of cellulose was accelerated. However, the number of bacteria such as Synergistia which could use VFAs also increased. As a result, the concentration of VFAs in the system was reduced and the acid-producing time was shortened. These results meant the increase of temperature could promote the degradation of cellulose in the anaerobic system and the VFAs production rate.