The microstructure and mechanical properties of a spray-deposited Mg-12.55Al-3.33Zn-0.58Ca-1.0Nd alloy under the hot extrusion condition were studied by XRD, OM, SEM, TEM and tensile tester. The results show that the spray-deposited as-extruded Mg alloy mainly consists of α-Mg matrix and Al2Ca phases. The matrix structure is equiaxed grain and the average grain size is about 3 μm. The Al2Ca phases with the grain size of about 1.0 μm, mainly distribute along the boundaries of the Mg matrix; furthermore, the twin structures exist in the Al2Ca phase. The σb, σ0.2 and δ of the Mg alloy reach 450, 325 MPa and 5%, respectively. Fracture morphologies show the massive stone-like Al2Ca phases, and it is the characteristic of intergranular fracture mode. Compared with conventional cast AZ91 alloy after hot extrusion, the spray deposited Mg-12.55Al-3.33Zn-0.58Ca-1.0Nd alloy possesses higher strength, but with poor ductility. High strength of the spray deposited Mg alloy is attributed to fine crystal strengthening and solution strengthening of Al and Zn atoms in the Mg matrix, while massive Al2Ca phases distributing along grain boundaries of the Mg matrix are responsible for the poor ductility in the Mg alloy.