Abstract: Marine engineering equipment faces significant challenges in achieving a coordinated design that integrates lightweight and properties with high strength and toughness under harsh service environments, such as those characterized by high salinity, high humidity, and impact loading. Traditional steel used in offshore platforms struggle to effectively balance the requirements of lightweight and mechanical properties. In contrast, Fe-Mn-Al-C lightweight high strength steels have emerged as highly promising alternative materials due to their lower density (10%-20% lighter than traditional steel), excellent strength and good weldability. Currently, under the "rolling + solution treatment" process route, the appropriate design of Al element content plays a crucial role in enhancing the properties of Fe-Mn-Al-C lightweight high strength steels. By employing characterization techniques, including optical microscopy(OM), scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD), the influence of Al element content on the microstructure and mechanical properties of the experimental steels during the staged preparation process was investigated. The results indicate that when the mass fractions of Al element are 5%, 8% and 12% respectively, the microstructure of the experimental steels after rolling treatment consists of austenite and ferrite phases. As the Al content increases, the morphology of austenite transitions from equiaxed to acicular, and the proportion of high-angle grain boundaries increases from 57% to 89%. When the Al element mass fraction is 8%, the rolled experimental steel exhibits the optimal strength-ductility balance, with a tensile strength of 747 MPa and an elongation of 28.3%. After solution treatment at 1 000 ℃, the comprehensive properties of the experimental steel with Al element mass fraction of 8% are further enhanced, achieving a tensile strength of 701 MPa, yield strength of 612 MPa, and elongation of 38.3%. Its fracture surface displays characteristic dimple patterns indicative of ductile fracture. Through optimization of Al element content and process control, precise design of the dual-phase microstructure in Fe-Mn-Al-C lightweight high strength steels have been realized, laying theoretical foundations for developing marine engineering steels.