In this study, the composition of fatty oil from Semen Ziziphi Spinosae and its cardiotonic activity on the heart isolated from a toad were studied. Oil-in-water (O/W) emulsions of fatty oil were prepared by the perfusion method. The fatty oil had a positive inotropic effect on isolated rat hearts at a concentration between 5 × 10(-3) and 2 × 10(-2) mL/10 mL, and the effect was in positive correlation with the concentration of calcium ions. In addition, this effect was inhibited by 2 mg/mL nifedipine, suggesting that the cardiotonic mechanism could be responsible for accelerating the inflow of calcium ions. Gas chromatography-mass spectrometry analysis showed that the main constituents of the fatty oil were 9-octadecenoic acid (43.32%), 9,12-octadecadienoic acid (42.57%), hexadecanoic acid (4.76%), 9-eicosenoic acid (2.95%), stearic acid (2.41%) and arachidic acid (0.81%). This preliminary study revealed that the fatty oil of Semen Ziziphi Spinosae exhibited remarkable cardiotonic activity in the tested models, and it is necessary to further reveal the effective substances of the fatty oil.