Abstract: The effects of aging temperature on the phase composition, microstructure and hardness of Fe-30Mn-12Al-0.9C low-density high-strength steel with high Al and high Mn content were studied.The microstructure evolution of the steel at different aging temperatures was analyzed by OM and XRD.The results show that there is little difference between the aged structure and the solid solution structure when aging at low temperature, which is mainly austenite+ferrite, there is nano level κ-carbide in the crystal, and the hardness change is small.When aging at 500℃, β-Mn appears in the tissue, and the hardness begins to increase.When the aging temperature reaches 650℃, the microstructure changes obviously, a large amount of β-Mn appears at the grain boundary, and the hardness increases obviously.When the aging temperature reaches 700℃, the austenite is completely decomposed into ferrite and κ-carbide, and with the accumulation and growth of β-Mn and κ-carbide at the grain boundary, the Rockwell hardness of the material reaches a maximum value of 66.3HRC.