Abstract: OBJECTIVE To establish a RP-HPLC method for the determination of the monosaccharide compositions and contents in polysaccharide of garlic. METHODS The garlic polysaccharide were derivatization with 1-phenyl-3-methyl-5- pyrazolone (PMP) after hydrolyzed into monosaccharides with 2 mol·L-1 H2SO4, monosaccharide derivatives were separated on Shimadzu VP-ODS volum (150 mm×4.6 mm, 5 μm) with acetonitril-Acetate buffer adjusted to pH 5.5 with Acetate (22∶78) as mobile phase and UV detection at 245 nm. RESULTS The content of monosaccharide compositions were measured in polysaccharide of garlic, molar ratio of mannose, rhamnose, glucuronide, galacturonicacid, glucose, galactose, arabinose was 4.31∶4.23∶4.19∶9.13∶27.4∶4.99∶3.81. CONCLUSION The methods is simple, sensitive, accurate and reliable. The method can be applied for the analysis of quality control and monosaccharide composition and molar ratio in polysaccharide of garlic.