Abstract: Microorganism plays an important role on all bio-degradation processes of organic matters． The paper illustrated the microbial species related to the generation of short-chain fatty acids ( SCFAs) during the anaerobic digestion ( AD) process and the relationship among these different microbes systematically，and discussed the influences of impact factors，i． e． ， sludge substrate，temperature，pH，carbon to nitrogen ratio and sludge retention time，on the biodiversity of acid-producing microbes，predominant microbial species and the production of the microorganisms． Meanwhile，the studies on the evolution of the different strategies to enhance the microbial activities of SCFA generation were introduced． Finally，in order to select the dominant microbial species related to SCFA generation during the sludge anaerobic digestion process，different strategies to regulate the impact factors were also investigated．