Oligosaccharide can be fermented at human colon by gut microbes to produce short chain fatty acids.This paper took isomalto-oligosaccharide(IMO) as carbon source to in vitro ferment with different gut microbiota that come from human feces.samples were collected at different time during fermentation to determine the volume and the types of short chain fatty acids.The results show that all of Bifidobacterium,Bacteroides,Enterobacteria,Lactobacillus and Enterococcus can utilize IMO to produce short chain fatty acids that are healthy for human body,but their volume and types are different.After 12 h fermentation,the volume of acetic acid is the most than other acids and however butyric acid and isobutyric acid are too little to determine.