The effect of samarium (Sm) adding (0, 0.5, 1, 1.5 and 2 wt.%) on the microstructure and mechanical properties of AZ61 magnesium alloy was investigated by OM, XRD, SEM and EDS. The results indicated that 0.4-2.2 vol.% Al2Sm particles with the average diameter of 1-7μm were found in AZ61 magnesium alloy with different Sm content addition. When rare earth element Sm content increased from 0 to 2.0 wt.%, the size of Al2Sm particles gradually increased and the content of β-Mg17Al12 was decreased. Meanwhile the grain size of AZ61-xSm magnesium alloy with solution treatment at 693K for 24h firstly decreased with Sm content increased to 1.0 wt.%, then gradually increased when Sm content excessed 1.0 wt.%. The maximum values of the ultimate tensile strength and the yield strength of AZ61-xSm magnesium alloys with solution treatment were 215 and 142 MPa, respectively, for the alloy with 1.0 wt.% Sm. And the maximum elongation (4.1%) of AZ61-xSm magnesium alloys was also achieved with 1.0 wt.% Sm addition.