The phase equilibria of the Mg-Pb-Zn ternary system were investigated using a combined methods of electron probe microanalyzer (EPMA), back scattered electron (BSE) and X-ray diffraction (XRD).Three isothermal sections of the Mg-Pb-Zn ternary system at 200 ℃, 300 ℃ (as seen in Fig.1) and 400 ℃ were experimentally established.The phase equilibria of Mg-Pb-Zn ternary system was thermodynamically assessed by using CALPHAD (Calculation of Phase Diagrams) method on the basis of the presently determined experimental data.A consistent set of thermodynamic parameters had been derived for describing the Gibbs free energies of each solution phase and intermetallic compound in the Mg-Pb-Zn system.The calcuiated phase diagrams and thermodynamic properties in the Mg-Pb-Zn systems was in good agreement with experimental data.The electrochemical behavior of Mg-Pb-xZn alloys in 3.5 wt.％ NaCl solution was investigated by electrochemical techniques and compared with AP65 alloy.The results show that Mg-Pb-xZn alloys after annealing at different conditions exhibit different discharge activity,good compositional homogeneity of magnesium matrix.This result reveals that annealing condition is an effective approach to improve the electrochemical performance of Mg-Pb-xZn alloy.The electrochemical cell was a three electrode cell with a Pt-counter and a saturated calomel reference (SCE) electrodes.The measurements of potentiodynamic polarization curves (scan rate: 5 mV·s-1, scan range:-2.5 to-0.8 V, as seen in Fig.2), galvanostatic curves (current density: 10 mA·cm2, 100 mA·cm2), electrochemical impedance spectra were measured in the frequency range 0.05～105 Hz with a 5mV ac signal at open circuit potential.