Microstructure and mechanical properties of FSP MB8（Mg-1.5Mn-0.3Ce）magnesium alloy were investigated under different processing parameters.Experiments adopted constant welding speed of 60 mm/min with rotation speed of 800

1200 and 1800 r/min.The results reveal that original coarse rolled MB8 is refined to be equixed and uniform grains after FSP as a result of severe stirring of the pin and occurrence of dynamic recrystallization in the SZs（stirring zones）.Average grain size in the SZs is greatly refined from 16.5μm to 6μm with rotation speed of 800 r/min.Ambient testing results show that the tensile strength is distinctly decreased with the great increase of elongation after FSP.Elongation of the alloy after FSP with 1200r/min reaches up to 57%

which is 160% of initial elongation.Tensile fracture morphology of the alloy was observed by SEM（scanning electron microscope）

and fracture mechanism was analyzed.