Abstract: OBJECTIVE To investigate the effect of 17-methoxyl-7-hydroxyl-benzofuran chalcone(YLSC) on sodium current in isolated ventricular myocytes of mouse. METHODS Acute isolation by enzymatic dissociation was used to obtain single myocytes through Langendorff retrograde aortic perfusion, INa was recorded before and after YLSC perfusion by the whole-cell patch clamp in voltage clamp mode. RESULTS YLSC blocked INa with the current-voltage (I-V) curve shifting upward, but the reversal potential and maximum activate potential of I-V curve were not changed by YLSC. The peak current density was obtain under the membrane voltage of -40 mV, and the peak density was decreased from(-22.31±2.20)pA/pF to(-10.64±0.97)pA/pF after perfusion with 400 μmol·L^-1 YLSC, the inhibition rate was (48.9±3.6)%(n=5, P<0.05). No significant change of the activation curve in the presence of 400 μmol·L^-1 YLSC was observed. The 50% of activation voltage of INa was changed from(-73.29±1.09)mV to (-76.79±1.62)mV and the slope was 2.43±0.36 to -11.45±1.91 in the presence of 400 μmol·L^-1 YLSC, which was no significant statistical meaning. The inactivation curve of INa had significant changed in the presence of 400 μmol·L^-1 YLSC. The 50% of inactivation voltage of INa was from (-73.29±1.09)mV to (-76.79±1.62)mV, and the slope was from -12.13±2.15 to -11.45±1.91(n=5, P<0.05). CONCLUSION YLSC can block the INa by accelerating steady-state inactivation voltage.