Ni-B-C powder prepared by ball milling was introduced to improve the electrochemical properties of new AB₃-type hydrogen storage alloy La_0.94Mg_0.06Ni_3.49Co_0.73Mn_0.12Al_0.20. X-ray diffraction(XRD) and scanning electron microscope(SEM) were adopted to investigate the phase structure and Surface morphology of the alloy. It suggests that the alloy remains the original LaNi₅ and La₂Ni₇ phases and some little particles appear on the surface of alloy. The addition of Ni-B-C improves the maximum discharge capacity and capacity retention rate. After adding a mass fraction of 10% Ni-B-C, the maximum discharge capacity increased from 346 mAh/g to 363 mAh/g, and the capacity retention rate after 50 cycles increases from 70% to 77%. The exchange current density I₀ and the limiting current density I_L reach 106 mA/g and 987 mA/g, respectively. Potentiodynamic polarization indicates the corrosion resistance of the electrodes is enhanced. The results show that the Ni-B-C powder can improve the comprehensive electrochemical properties of the hydrogen storage alloy.