Objective To establish a method for the determination of monosaccharide composition in Anoectochilus Roxburghii polysaccharide(ARPS)by pre-column derivatization High Performance Liquid Chromatography(HPLC). Methods ARPS was hydrolyzed by trifluoroacetic acid(TFA)solution and the monosaccharide derivatives obtained with 1-phenyl-3-methyl-5-pyrazolone(PMP)were separated by HPLC using gradient elution process. The pH, dosage of PMP in the process of derivatization and concerntration of TFA in the process of hydrolyzation was optimized respectively. Results ARPS was composed of mannose, ribose, glucose, galactose and arabinose, and their molar ratio was 1.00:8.47:47.30:1.17:1.19. Conclusion The method is simple, workable and had good reproducibility. It could be used to determine the monosaccharide composition of ARPS.