Endo-inulinase can selectively hydrolyze inulin to form fructooligosaccharides.Fructooligosaccharides has attracted much more attention in the industrial application due to its attractive features such as modifying gut microbial population,non-cariogenic,lowing total cholesterol and lipid in the serum,stimulating immune function and harmless to health,so it is known as prebiotics.In this paper,we discuss the functions and production of fructooligosaccharides,and particularly,we focus on the activity assay,properties,molecular biology,and application of endoinulinase,which is in favour of developing fructooligosaccharides in the application of foodstuff.