Mg-based hydrogen storage alloys Mg67-xCaxNi33 (x=0, 5, 10, 15, 20, at%) were prepared by means of induction melting，melt-spinning and ball milling. The effects of Ca content and preparation technologies on phase composition and hydrogen storage properties were studied. The results show that the preparation technologies (as-cast, casting + ball milling and casting + melt-spinning + ball milling) have little effect on the phase composition. The alloys containing Ca can form amorphous after melt-spinning. Mg67Ni33 alloy are mainly composed of Mg2Ni and a little quantity of Mg. The content of Mg2Ni decreases, while MgNi2 and Mg2Ca increase with the increase of Ca content in Mg67-xCaxNi33 alloys. When Ca content reaches 20at%, Mg47Ca20Ni33 alloy mainly consist of MgNi2 and Mg2Ca phase. P-C-T tests show that the maximum hydrogen storage capacity of Mg67-xCaxNi33 alloys decreases with increase of Ca content due to the decrease of Mg2Ni phase. After hydrogen absorption, Mg67Ni33 consists of Mg2NiH4 phase, while Ca containing alloys Mg67-xCaxNi33 alloys consist of Mg2NiH4, CaH2 and MgNi2