A new HPLC-UV technique for the separation and analysis of 10 monosaccharides achieved within 13.5 min using 1-phenyl-3-methyl-5-pyrazolone (PMP) as the labelling molecule of the reductive  monosaccharides has been established by combining common high performance liquid chromatography-UV and C₁₈ column.  The established technique was applied to the quantification of the monosaccharide components  in extract of Silybum marianum.  The results showed that the tested 10 monosaccharides as PMP derivatives were baseline separated under the HPLC conditions proposed.  It was confirmed that Silybum marianum   extract was composed of mannose, rhamnose, glucuronic acid, galacturonic acid, glucose, xylose, galactose and arabinose with the molar ratio of 0.66∶0.84∶0.58∶1.0∶1.6∶0.69∶2.7∶4.8.  Quantitative recoveries of the compositional monosaccharides separated from the extract were in the range of 92.4% − 104.0%, and the RSD values fell within 0.68% − 3.81%.  The results demonstrated that the proposed HPLC method was simple, rapid, convenient, and precise, and it was applicable to the analysis of the compositional monosaccharides of Silybum marianum extract.