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Microstructure,mechanical properties and corrosion resistance of as-cast and as-extruded Mg-4 wt％ Zn-1 wt％ La magnesium alloys were investigated.The alloys were produced by low-pressure die casting method and extruded at 350 ℃ after homogenization at 400 ℃ for 24 h.The results show that the as-cast alloy mainly consists of primary α-Mg matrix and Mg-Zn-La ternary second phases (also called T-Phase) along grain boundaries and isolated spherical particles inside the grains.After extrusion at 350 ℃,the average grain size decreases by 81％ due to dynamic recrystallization mechanism and T-phase particles are distributed along the extrusion direction.The elongation,yield strength and tensile strength of the as-cast Mg-4Zn-1La alloy increase by 179％,90％ and 40％,respectively,as a result of the extrusion process.The as-extruded Mg-4Zn-1La alloy shows better corrosion resistance than the as-cast alloy due to increased grain boundaries and decreased content of T-phase.