Abstract: Nerium oleander L. is an evergreen shrub in the dogbane family Apocynaceae and planted throughout the tropical region. It has cardiotonic, antioxidant, anti-inflammatory and anticancer activities. Nerium oleander L. has high amount of cardiac glycoside and flavonoids compounds. From methanol extract of flowers of Nerium oleander L. grown in vietnam, it has been isolated four compounds. Their structures were identified as (1) D16-Dehydroadynerigenin, (2) D16-Digitoxigenin, (3) Quercetin and (4) Kaempferol on the basis of spectroscopic data and by comparing their physicochemical and spectral data with those published studies. The effect of fraction HF2, which containing compound 1 and 2 on heart function was examined, revealing potent positive inotropic effect on isolated rabbit heart by increasing the contractility and coronary flow heart but does not alter heart rate.