Abstract: GC-MS was used to determine the concentrations of jasmonic acid (JA), indole-3-acetic acid (IAA) and abscisic acid (ABA) in Populus canescens leaves in this paper. Abundant cold methanol (80%, v/v) was used to extract JA, IAA and ABA, and three internal standards, D3-ABA 300 ng,13C6-IAA 60 ng and DHJA 80 ng were simultaneously introduced into the leaf samples. Crude extract was condensed by vacuum evaporating and hormones were re-extracted by ethyl acetate at pH 2.5--3.0 (×3). Then condensed JA, IAA and ABA extracts were purified by Sep-Pak C18 columns. Thereafter, partially purified hormones were methylated using trimethylsilyldizomethane and then analyzed by GC-MS (JA and ABA). IAA was analyzed by GC-MS after an additional TMS reaction. Results showed that concentrations of ABA, JA, and IAA in leaf tissues of P. canescens were 121.064--128.771 ng/g, 2.190--6.974 ng/g and 4.990--15.012 ng/g Fw, respectively. In concentration in P. canescens leaves, ABA IAA JA.