Abstract: Scanning electron microscopy (SEM) and compressive tests at room temperature and elevated temperatures were used to investigate the effect of Ni/Ti atom number ratio on the microstructures and mechanical properties of Ni_42+xTi_50-xAl₄Hf₄ (x=0-7) alloys. It is found that Ni_42+xTi_50-xAl₄Hf₄ alloys are composed of NiTi and Ti₂Ni phases. The size and volume fraction of Ti₂Ni phase decrease rapidly and the precipitation strengthening effect weakens with increasing Ni/Ti values. At room temperature when the Ni/Ti ratio increases, the compressive yield strength (σ_0.2) and Vickers hardness (Hv) of the alloys decrease, but the ductility increases. At elevated temperatures, for the alloys of Ni/Ti < 1, the precipitation strengthening of Ti₂Ni phase plays the major role, resulting in a decrease of σ_0.2 with increasing Ni/Ti values; but for the alloys of Ni/Ti > 1, the solid solution strengthening effect of Hf improves, and the uniform distribution of Ti₂Ni is more favorable for the strength, leading to the increase of σ_0.2 with increasing Ni/Ti values. The high-temperature yield strength is asymmetrical with a deviation from stoichiometry (Ni/Ti=1).