Equal-channel angular pressing (ECAP) was conducted on Mg-1.5Mn-0.3Ce magnesium alloy at 623 K using route Bc to investigate its microstructure, the texture and mechanical properties. The microstructure observation indicates that grains are obviously refined by ECAP, the smallest grain size of ECAPed magnesium alloy is about 1.2 μm after sixth pass ECAP from 26.1 μm of as-rolled one, and numbers of tiny Mg12Ce dispersively distribute in intragranular and intergranular regions. At the same time, the texture of as-rolled magnesium alloy is reduced gradually and starts to change to ECAPed texture when the texture intensity rises with the increase of ECAP passes. Mechanical properties show that the tensile strength and yield strength are raised with ECAP passes before three passes, matching the relationship of Hall-Petch because grain refinement is more significant than texture softening, and gets the maximum values of 272.2 MPa and 263.7 MPa at the third pass deformation. When the passes continue to increase to four passes, the strength is declined in contradiction to Hall-Petch relationship due to formed non-basic texture. The tensile-to-failure morphologies reveal that fractured mode is along the grain boundary for as-rolled and ECAPed magnesium alloys, and there are more dimples for sixth pass with the biggest elongation of 16.8 % at room temperature.