The La0.7Mg0.3(Ni0.85-xCo0.15Alx)3.4 hydrogen storage electrode alloys were prepared by cold crucible melting under argon gas atmosphere. The phase structure of these alloys and the electrochemical properties and surface of corresponding electrodes were investigated by means of XRD and tri-electrode test system and SEM. Rietveld analyses show that all these alloys consist of hexagonal Ce2Ni7-type main-phase,hexagonal CaCu5-type phase,rhombohedral PuNi3-type phase,cubic MgCu2-type Laves-phase and orthorhombic BCr-type phase. The Ce2Ni7-type main-phase content and the cell volume of all these phases increase with increasing of x. P-C isotherms show that hydrogen-desorption plateau region narrows,and the plateau pressure decreases and the plateau becomes steeper with increasing of x. The electrochemical results show that maximum discharge capacity and high-rate dischargeability decrease,cyclic stability is improved markedly with increasing of x.