The Mg–5Al–2Ca alloys reinforced by 2 vol.%, 5 vol.% and 10 vol.% 5μm SiCp were fabricated by stir casting. The cast composites were subject to hot extrusion. In the cast composites, addition of SiCp disturbs the network distribution of Al₂Ca phase along grain boundaries. After extrusion, grains of the matrix are refined further and the Al₂Ca phase broke into particulates. Moreover, the Al2Ca phase and grain size can be further refined by the addition of SiCp. As compared with monolithic Mg–5Al–2Ca alloy, the addition of SiCp conduces to obvious improvement of TYS and work hardening rate, however, at the expense of elongation. Unlike the TYS, the UTS of SiCp/Mg-5Al-2Ca composite does not change monotonously with increasing SiCp’s content, the highest UTS appears when the SiCp’s volume fraction is 5%. The interfacial debonding between SiCp and Al₂Ca phase and cracked particles are considered as the main crack source for SiCp/Mg–5Al–2Ca composite.