The Mg–Ca alloys with 2wt%, 3wt%, 5wt% Al content were fabricated in this paper. After be extruded at 673K with the ratio of 16:1, the microstructures and mechanical properties of the alloys influenced by Ca/Al ratio were investigated.Results showed that the category and amount of precipitated secondary phase were influenced obviously by Ca/Al ratio, which changed from Mg2Ca and (Mg, Al)2Ca to Al2Ca as the Ca/Al ratio decreased from 1 to 0.4. Even though the secondary phase was cracked after the application of hot extrusion, the amount, size and distribution of secondary phase were strongly dependent on Ca/Al ratio. The basal plane texture was found in all the as-extruded alloys, the I(101¯0)/I(101¯1) and I(0002)/I(101¯1) values demonstrated different changing tendencies with the variation of Ca/Al ratio. All the UTS, elongation and strain hardening rate of the as-extruded alloys increased with decreasing Ca/Al ratio, however, the YS exhibited the inverse variation tendency. A significant stagnation point was found in the θ-(σ-σ0.2) curve as the Ca/Al ratio is 1, which becomes unobvious with decreasing Ca/Al ratio. The reasons are given and analyzed.