Abstract: To study the angiosperm pectin monosaccharide components and content in primary cell wall as well as its relation with plants systematics between dicotyledon and monocotyledon, gas chromatograph\|mass spectrometry (GC/MS) was performed to detect the pectin monosaccharide components and content in 22 angiosperms and the data were analyzed by principal component analysis (PCA), Students test and ShannonWeiner index analysis. Seven monosaccharides were found in angiosperm pectin including xylose, rhamnose, fucose, arabinose, galactose, glucose and mannose. The pectin was particularly rich in rhamnose, arabinose and galactose, but with little fucose and mannose. Five pectin monosaccharides were screened from 22 plants by PCA, and they were xylose, arabinose, rhamnose, galactose, and glucose respectively. Twodimensional chart and Students test showed that the significantly different content of xylose or galactose in pectin could provide a reference for distinguishing class dicotyledon from class monocotyledon (P＜0.01). The ShannonWiener index showed the more diversities of monosaccharide in dicotyledon than monocotyledon (P＜0.01). Taken together, the different content of pectin monosaccharide could provide a reference for the angiosperms systematics between dicotyledon and monocotyledon.