With the laser remelting of cast alloys combined with non-equilibrium liquidus projection thermodynamic calculations, a high-strength and heat-resistant Al-3Fe-2Mn alloy was designed. Incorporating Mn atoms into the metastable nanoscale Al₆Fe phase, occupying some lattice sites, enhances its thermal stability. Additionally, during rapid solidification of laser powder bed fusion (L-PBF), the solubility of Fe and Mn elements in the aluminum alloy increases significantly, forming a supersaturated solid solution with improved strength. This alloy demonstrates excellent processability, achieving a relative density of over 99%, and tensile strengths of 295 MPa at 200 °C and 230 MPa at 300 °C. The Al-3Fe-2Mn alloy holds great potential for wide applications due to its high strength at high temperature.