The AlCrMoNiTi high entropy alloy was prepared by powder metallurgy process. Its microstructure and hardness of as-cast and annealed state were studied. The results show that the as-cast alloy exhibits a mixture of the dendrite (Cr, Mo)-rich bcc phase and the interdendrite (Al, Ni, Ti)-rich fcc phase. The aged alloy can obtain a peak hardness HV of 6150 MPa at 900 oC, and then anneal softening occurs at 1000 oC, but its hardness HV still maintained at a high level of 5160 MPa. This shows that the AlCrMoNiTi alloy exhibits a good high-temperature age hardening performance. Age hardening of the alloy is mainly attributed to the grain refinement strengthening at 800 oC and the precipitation hardening of the second phase (bcc2) at 900 oC. The disappeared second phase and grain coarsening are the main reasons for the softening anneal at 1000 oC.