Mg-6Zn-xCe (x =0,0.6,1.0,2.0) alloy ingots with diameter of 50 mm were extruded into bars with diameter of 12 mm at 300 ℃.The microstructures were analyzed by X-ray diffraction,optical microscopy,scanning electron microscopy and transmission electron microscopy,and mechanical properties were tested at room temperature.The results showed that major intermetallic composition in as-cast Mg-6Zn and Mg-6Zn-0.6Ce alloys was Mg4Zn7 phase,during extrusion Mg4Zn7 phase was dissolved into matrix and then precipitated as MgZn2.In as-cast and as-extruded Mg-6Zn-lCe and Mg-6Zn-2Ce alloys the major intermetallic composition was T phase.The microstructure of as-extruded alloy was refined due to complete dynamic recrystallization,the average grain size decreased with increasing Ce content,which were 12.1,11.7,11.0 and 10.0 μm,respectively.High density MgZn2 precipitated in Mg-6Zn and Mg-6Zn-0.6Ce alloys.The broken T phase particles were distributed linearly along extrusion direction.Mg-6Zn-0.6Ce alloy exhibited a high yield strength of 226.3 MPa that was about 24 MPa higher than Mg-6Zn alloy.However,with increasing Ce contents,the strengths were decreased slightly because the effects of precipitation strengthening of MgZn 2 and solid solute strengthening of Zn were weakened though the strengthening effect of T phase was enhanced.