In this paper, the electrochemical properties of MlNi4.3-xCoxA10.7electrode alloys, including high rate dischargeability, exchange current density 10, limiting current density IL, and diffusion coefficient of hydrogen in the hydride Da by means of linear polarization, anodic polarization, and electrochemical impedance spectroscopy were systematically studied. The results indicate that, with the increase of Co content, the cyclic stability is improved markedly, which agrees with previous investigation. However, activation becomes more difficult, and the high rate dischargeability decreases. The linear polarization and anodic polarization results suggest that the exchange 21 current density I0 and limiting current density IL decrease from the 395 (x=0) to 33mAg (x=1.3) and from 2263 (x=0) to 308mA g-1, respectively. The electrochemical impedance spectroscopy result also reveals that the diffusion coefficient of hydrogen in the alloys decreases rapidly with the increase in Co content in MlNi4.3-xCoxAl0.7 hydride alloy electrodes.