For the investigation of medicinal resources in Crataegus species, the present study was carried out to evaluate the pharmaco-constituents in the leaves of Crataegus Pinnatifida var. psilosa (Rosaceae). Fruits has folk medicine in Korea. From the $Et_{2}$O fraction of MeOH extract, a new compound, apigenin-8-C-(6"-acetyl)-$eta$-D-glucopyranoside, named psilosin and three known compounds, ursolic acid, phytosterol complex and (-)-epicatechin were isolated and identified on the basis of their physico-chemical properties and spectroscopic evidences (UN, IR, NMR and mass etc.) in comparison with authentics, respectively.