Abstract: Objective: To compare the chemical composition of water extract in Radix Pseudostellariae from different areas with multivariate staticstical based on UPLC- Triple TOF- MS / MS.Peak matching,peak alignment and noise filtering were used in analyzing mass spectrometry data. Accurate m / z value analysis of MS data based on software of database search and MS / MS fragment analysis were applied to constituents identification. Data processing using PCA and PLS- DA to investigate the difference of chemical composition in the water extract of Radix Pseudostellariae from different habitats. The results showed that material mainly contains amino acids,nucleosides,sugar,organic acids and other 17 kinds of chemical constituents in Radix Pseudostellariae water extracts,the main component wasarginine. The differences of chemical components in water extract of Radix Pseudostellariae from 4 different habitatswere distinct.Isobutyrylglycine,Guanine and Adenosinewere greater in Radix Pseudostellariae from Zherong,Fujian; the sample from Shibing,Guizhou contained more material in Uridine-5 '- monophosphate and Isomaltose; the sample from Xuancheng,Anhui contained more material in Arginine,Dodecanoic acid,5- methyl cytosine,L- glutamic acid,L- Histidine and Phenylalanine,and the water extract of Radix Pseudostellariae from Jurong Jiangsu contained more Melatonin.