A series of multi-component MI-based hydrogen storage alloys with a cobalt atomic ratio of 0.40-0.75 w ere prepared. The electrochemical properties under different charge-discharge conditions and PCT characteristics measured by electrochemical method were investigated. The addition of other alloying elements for partial substitution of Co lowers the hydrogen equilibrium pressure and discharge capacity, but improves the cycling stability and makes the alloys keep nearly the same rate discharge capability and high-temperature discharge capability as those of the compared alloy.The reasons were discussed.