The influence of the heat treatment on mechanical properties and microstructures of the Fe-22Mn-0.6C high-manganese steel was investigated at different annealing temperatures. A high-Mn TWIP (Twinning Induced Plasticity) steel specimens (0.6C, 24Mn steel) were fabricated, and were annealed at 700, 900, and 1100 degrees C for 150 min and then air-cooled. The carbide precipitates in the microstructure of specimens were annealed at 700 degrees C. However, the microstructure of specimens annealed at 900 and 1100 degrees C is austenite and some grains include annealing and mechanical twins. The results show that tensile strength of the material decreased, and the ductility of material was improved with increasing annealing temperature. Besides that, hardness value decreased between 700 and 1100 degrees C, which shows a good agreement with the equilibrium dissolution temperature of M3C carbides.