The effects of Ce and Zn addition on the microstructures and mechanical properties of Mg-1.3Mn-based alloys were studied. The Ce and Zn addition refined both the as-cast and the heat treatment grain structure of the Mg-1.3Mn alloy. Moreover, the tensile strength and Brinell-Hardness were enhanced. The fracture mechanism of Mg-1.3Mn-1.0Ce-xZn alloys changed with the increase of Zn addition.