In this study, three triterpenoids, two steroids and nine flavonoids were isolated from the leaves of Alnus firma Sieb. et Zucc. On the basis of spectroscopic evidences, the structures of these compounds were established as ${eta}$-amyrin acetate, ${eta}$-amyrin, ${eta}$-sitosterol, alnustic acid methyl ester, ${eta}$-sitosterol glucoside, pinocembrin, alnustinol, quercetin, quercetin-3-O-${alpha}$-L-arabinofuranoside, quercetin-3-O-${alpha}$-L -rhamnopyranoside, quercetin-3-O-${eta}$-D-glucopyranoside, myricetin-3-O-${eta}$-D-galac-topyranoside, (+)-catechin and (-)-epicatechin.