To explore a rapid identification of monosaccharide composition of polysaccharide from Rhizoma Coptidis through HPLC-MSn. Methods:After being extracted, separated, removed of protein and pigment, Rhizoma Coptidis polysaccharide was obtained from Rhizoma Coptidis. Polysaccharides of Rhizoma Coptidis was hydrolyzed with the TFA of 2 mol.L-1. 1-phenyl-3-methyl-5-pyrazolone (PMP) was used as derivatization reagent. And high performance liquid chromatography-mass spectrometry (HPLC-MSn) was used to identify the composition of monosaccharide, and the resolve fragmentation regularity of its derivatives was analyzed. Results:Through analysis, the monosaccharides of polysaccharides from Rhizoma Coptidis were mannose, ribose, rhamnose, galacturonic acid, glucose, galactose, arabinose/ xylose, fucose, among which ribose and fucose were the first reported monosaccharides that obtained from polysaccharide of Rhizoma Coptidis. Conclusion:HPLC-MSn has a guiding significance in analyzing the monosaccharide composition of polysaccharides from Chinese materia medica.