Equal channel angular pressing (ECAP) was applied to commercial pure magnesium alloy, Mg-1wt%Si alloy and Mg-4.2wt%Zn-0.7wt%Y alloy. With increasing ECAP passes, both tensile strength and ductility of the alloys are increased, which are mainly resulted from the grain refinement. At the same time, for the Mg-Zn-Y alloy with inherent low damping capacity, damping capacity is increased after ECAP passes, however, the damping capacity is still low even after 6-pass ECAP. While for the commercial pure magnesium and Mg-Si alloy with inherent high damping capacity, although the damping capacity is decreased obviously after ECAP, Q-1 is still greater than 0.01. The damping capacity after ECAP processing is mainly influenced by grain size and deformation microstructure. ECAP paves a way for the development of magnesium alloys with high strength and high ductility combined with high damping capacity.