Abstract: The cast Mg-3.4Al-2Ca alloy was firstly treated by solid solution heat treatment and then by hot extrusion deformation. The effects of solid solution heat treatment on the microstructure of cast and extruded alloy and mechanical properties of extruded alloy were investigated. The results show that, compared with the nosolution treatment, the substable(Mg,Al)₂Ca phase can be transformed into stable Al₂Ca phase by high temperature solution treatment. The alloy is completely recrystallized after extrusion and the grain is fine and uniform, the Al₂Ca second phase is broken into granular form and a large number of submicron Al₂Ca are distributed in the alloy. The yield strength, tensile strength and elongation of the solid solution treated and extruded alloy companed with that of only solution treatment alloy increase by 25.0%, 9.5% and 15.1%,respectively.