A new dammarane-type triterpenoid, betulafolianediol, $C_{30}$H$_{52}$O$_{3}$, mp $165^{circ}$[${alpha}$]$_D$^{20}=+$20^{circ}$, was isolated form the unsaponifiable fraction of leves of Betula latifalia $K_{OMAROV}$ (Betulaceae). From the spectral data of the betulafolianediol and its derivatives, betulafolianediol monoacetate (II) and betulafolianediol monoketone, the structure of betulafolianediol was provide to be 3${alpha}$, 25-dioxy-dammarane-20[S]->24 [S]-epoxide.