Abstract: The Mg‒5.5Zn‒0.1Y alloys reinforced by the nanoscale SiC particles were prepared by solid phase synthesis, and the effect of SiC particle mass fraction on the microstructure and mechanical properties of Mg‒5.5Zn‒0.1Y alloys was investigated. The results show that, the distribution of SiC particles becomes more uniform with the increase of SiC particle mass fraction, which results in the significant napping and grain refinement. A large number of dislocations occur in the vicinity of SiC particles in the Mg‒5.5Zn‒0.1Y alloys doped by SiC particles in the mass fraction of 2.0%, which provide the favorable conditions for the recrystallization nucleation and promote the grain refinement. Increasing the SiC particle mass fraction can increase the hardness of alloys. When the SiC particle mass fraction is 2.0%, the Mg‒5.5Zn‒0.1Y alloys achieve the maximum hardness as HV 82. When the SiC particle mass fraction is increased, the number of cracks is reduced, the interface between the SiC particles and Mg‒5.5Zn‒0.1Y alloys is de-bonded, the crack source is formed, and the fracture is caused. The higher SiC particle mass fraction can make the alloys obtain the higher strength and elongation.