Mg-Al-Ni alloys were prepared by powder metallurgy, and their microstructure and elevated temperature mechanical properties were investigated. Results indicate that, in addition to α-Mg matrix, both coarse Al_3Ni_2 particles and fine Al Ni nano-particles exist in the Mg-Al-Ni alloys. The strength at 150?C is improved with the increase in Ni content. Mg-18.3Al-8Ni alloy possesses a compressive strength of234.7 MPa and a yield strength of 146.5 MPa. Plasticity is also improved with a low concentration of Ni. Mg-11.3Al-2Ni alloy possesses a compression ratio of 17.3%. The phases of Al_3Ni_2 and Al Ni in the alloys block the movements of grain boundaries and dislocations during the deformation at elevated temperature. The existence of Al Ni phase provides a non-basal slip system, leading to the improvement in plasticity. Finally, the formation mechanism of Al-Ni phases in the process is discussed with thermodynamics and kinetics. Mg-Al-Ni alloys were prepared by powder metallurgy, and their microstructure and elevated temperature mechanical properties were investigated. Results that, in addition to α-Mg matrix, both coarse Al_3Ni_2 particles and fine Al Ni nano-particles exist in the Mg -Al-Ni alloys. The strength at 150? C is improved with the increase in Ni content. Mg-18.3Al-8Ni alloy possesses a compressive strength of 234.7 MPa and a yield strength of 146.5 MPa. The concentrations of Ni. the phases of Al_3Ni_2 and Al Ni in the alloys block the movements of grain boundaries and dislocations during the deformation at elevated temperature. The existence of Al Ni Finally, the formation mechanism of Al-Ni phases in the process is discussed with thermodynamics and kinetics.