Abstract: The methanol extract of the dried leaf of Calophyllum polyanthum was partitioned successively with petroleum ether and ethyl acetate.Petroleum ether fraction was gradient eluted over silica gel column using 9:1 petroleum ether- ethyl acetate as eluant to give a rod crystal and three known compounds.The rod crystal was characterized by IR,1H NMR,13C NMR,MS and X-ray single crystal diffraction.The results showed that the crystal was friedelin-3,4-lactone,and the molecular formula was C30H50O2. Its bioactivity was measured by MTT assay.The results proved that triterpenoid lactone has a promotion effect on the inducing proliferation of rat mesenchymal stem cells(rMSCs).