Abstract: ZnO nanoparticles were prepared from H₂C₂O₄·2H₂O and Zn(Ac)₂·2H₂O,and characterized by transmission electron microscope(TEM) and X-ray diffraction(XRD).Obained ZnO nanoparticles were used to fabricate a mixed carbon paste electrode.The electrochemical investigation of haemachrome chloride on a nano-ZnO mixed carbon paste electrode was conducted with cyclic voltammetry and differential pulse voltammetry.Compared to the commercial ZnO particles and the bare carbon paste electrode,the ZnO nanoparticle mixed carbon paste electrode possesses electrocatalytic properties toward haemachrome chloride due to the significant increase of peak current and the negative shift of peak potential.After accumulation at -0.30 V for 30 s in the phosphate buffer at pH=9.18,a sensitive reduction peak located at -0.44 V was employed for the determination of haemachrome chloride.Under optimum conditions,the reduction peak current was proportional to haemachrome chloride concentration in the range of 3.1 ×10^-9~3.1 ×10^-7 mol/L,with a detection limit of 1.5 × 10^-9 mol/L.The proposed method was successfully applied to the determination of haemachrome chloride in haematic tonic(Red hearts K).