In order to improve the hydrogen storage capacity and the activation properties of the hydrogen storage alloys, the rare-earth metal alloy series, MmN <TEX>$i_{4.5}$</TEX>M <TEX>$n_{0.5}$</TEX>Z <TEX>$r_{x}$</TEX>(x=0, 0.025, 0.05, 0.1), are prepared by adding excess Zr in MmN <TEX>$i_{4.5}$</TEX>M <TEX>$n_{0.5}$</TEX> alloy. The various parts in hydrogen storage vessel consisted of copper pipes reached the setting temperature within 4~5 minutes after heat addition, which indicated that storage vessel had a good heat conductivity required in application. The performance test on storage vessel filled with rare-earth metal alloys of 1000 gr was also conducted after hydrogen charging for 10 min at <TEX>$18^{\circ}C$</TEX> under 10 atm. It showed that the average capacity of discharged hydrogen volume was found to be for <TEX>$MmNi_{4.5}$</TEX> <TEX>$Mn_{0.5}$</TEX> and <TEX>$MmNi_{4.5}$</TEX> <TEX>$Mn_{x}$</TEX> 0.5/<TEX>$Zr_{samples}$</TEX> indicated that the released amount of hydrogen for this <TEX>$AB_{5}$</TEX> type alloys was more than 92 % of theoretic value, and also it was found that the optimum discharging temperature for obtaining an appropriate pressure of 3 atm was determined to be <TEX>$V^{\circ}C$</TEX> for <TEX>$MmNi_{4.5}$</TEX> <TEX>$Mn_{0.5}$</TEX><TEX>$Zr_{x}$</TEX>(x=0, 0.025, 0.05, 0.1) hydrogen storage alloys. The released amount of these hydrogen storage samples was 125 <TEX>$\ell$</TEX> , 122.4 <TEX>$\ell$</TEX> and 108.15 <TEX>$\ell$</TEX>/kg for <TEX>$MmNi_{4.5}$</TEX> <TEX>$Mn_{0.5}$</TEX> <TEX>$Zr_{0.025}$</TEX> <TEX>$MmNi_{4.5}$</TEX>M <TEX>$n_{0.5}$</TEX>Z <TEX>$r_{0.05}$</TEX>, and MmN <TEX>$i_{4.5}$</TEX> Mn_0.5<TEX>$Zr_{0}$</TEX>, at <TEX>$70^{\circ}C$</TEX> respectively. Amount of the 2nd phases increase with increase on Zr contents in <TEX>$MmNi_{4.5}$</TEX><TEX>$Mn_{0.5}$</TEX> <TEX>$Zr_{ 0.1}$</TEX>/ alloy. This phenomenon indicates that<TEX>$ ZrNi_3$</TEX> in <TEX>$MmNi_{4.5}$</TEX> <TEX>$Mn_{0.5}$</TEX> <TEX>$Zr_{x}$</TEX> / phase, which shows the maximum storage capacity and the strong resistance to intrinsic degradation, is considered as a proper alloy for hydrogen storage. As the Zr contents increase, the activation time and the plateau pressure decreases and sloping of the plateau pressure increases.creases.eases.s.