The reduction of malondialdehyde (MDA) on hanging mercury drop electrode was studied by 2.5th order differential voltammetry.The linear response range of current (e″) against the concentration of MDA was given from 1.0×10^-6 to 1.0×10^-3 mol/L in the condition of a base solution of 0.1 mol/L NH₄Cl at scanning rate of 80 mV/s. The detection limit was 1.0×10^-7 mol/L. The method provids succesfully a rapid and simple way to determine the concentration of MDA in the sample of cardiac myocytes.