Objective Effect of hawthorn and melanoidins on the in-vitro growth of Bifidobacterium and E.coli. Methods According to methods of the Chinese pharmacopoeia (2015),the charred hawthorn was prepared. The melanoidins in charred hawthorn were separated and purified by the macroporous resin extraction process. Ultraviolet spectrophotometry was used to detect melanoidins. The gas chromatography was used to detect the effects of hawthorn, charred hawthorn and melanoidins on the content of the acetic acid in Bifidobacterium and E.coli during growth, stable and decay period. Results In the early stage, the effects of hawthorn and charred hawthorn on bacteria were greater than melanoidins. In the middle and late stage, melanoidins inhibited the growth and metabolism of E.coli by changing the generation of acetic acid, and contributed to that of Bifidobacterium and also promoted the generation of acetic acid and regulate the intestinal flora. Conclusion Hawthorn, charred hawthorn and melanoidins all promote digestion by promoting the growth and metabolism of intestinal flora. Among them, charred hawthorn has a better effect on intestinal flora.