In order to investigate the effect of annealing treatment on microstructures and mechanical properties of CrCuFeMnTi high entropy alloy, the as-cast CrCuFeMnTi alloy ingot was prepared by vacuum arc melting under the argon protection, and then the microstructures observation and mechanical properties testing of alloy samples under annealing treatment at different temperatures were performed. The results show that the as-cast CrCuFeMnTi alloy is composed of a hexagonal close packed and a face centered cubic solid solutions, and typical microstructures with dendrite and interdendrite phases are observed. The element diffusion and morphologies homogenization mainly proceed when the annealing temperature is under 750℃, and the hexagonal close packed phase would transforms into body centered phase after alloy annealed at 900℃. This phase transition is caused and controlled by the element diffusion. The hardness and strength of alloy are all improved when alloy is annealed at below 750℃, meanwhile, the alloys all show the brittle fracture character.