A series of Ti-B complexes with different composition and Mg45Ti3V2Ni50 hydrogen-storage alloys were synthesized by ball-milling. The effect of modification of Ti-B complexes on the cycle stability of Mg45Ti3V2Ni50 alloys was discussed and the Ti3B4 with a better comprehensive modification effect for Mg45Ti3V2Ni50 alloy electrode was selected. Mg45Ti3V2Ni50 -alloy electrode was modified with different mass ratios of Ti3B4 by ball-milling. The results show that the improvement degree of cycle stability and persistence is different due to different ratios of modification. There is a best composition of Ti-B and ratio of modification in the surface-modification process of Ti-B for the Mg-based hydrogen storage alloys in order to improve the cycle stability