Abstract: Two fatty acid monoglycerides were isolated from the petroleum ether fraction of the stem and leaves of Ligusticum chuanxiong by using MCI column, silica gel column, Sephadex LH-20 column and semi-preparative HPLC. Their structures were elucidated by 1D-NMR, 2D-NMR, HR-ESI-MS and optical rotation data. One of them is a new compound, named 14,15-dehydrocrepenynic acid monoglyceride (1), the other was a known compound (R)-α-(7'Z,10'Z,13'Z)-hexadecatrienoic acid monoglyceride (2), both of which were isolated from Ligusticum chuanxiong for the first time. The results of in vitro antitumor activity assay showed that compounds 1 and 2 could inhibit the proliferation of MCF-7 with IC₅₀ values of 30.75 and 36.82 μmol·L^-1, respectively.