Abstract: A novel heat-resistant steel with three different aluminum contents（2.96 wt%, 4.16 wt% and 5.14 wt%）was designed and fabricated based on Incoloy 800H high-temperature alloy, the microstructure and mechanical properties of the heat-resistant steels were investigated by XRD, OM, SEM, EDS and EPMA techniques. The influencing mechanism of aluminum content on the tensile behavior at room temperature was explored through room-temperature tensile tests. The results show that the casting microstructure of the heat-resistant steels consists of austenitic matrix and network of precipitates. In the casting sample with an aluminum content of 2.96 wt%, the network of precipitates comprise of Ni Al phase and M₇ C₃ carbides enriched in titanium and chromium. The network of precipitates in the casting samples with aluminum contents of 4.16 wt% and 5.14 wt% consist of Ni Al phase. As the increase of aluminum content, the quantity of brittle Ni Al phase precipitates at grain boundaries increases, leading to gradual enhancement in the hardness and tensile strength of the heat-resistant steels,accompanying a reduction in elongation. The sample with aluminum content of 5.14 wt% exhibits the highest ultimate tensile strength of 819.28 MPa, albeit with compromising elongation of 14.52%. At 800 ℃, with the increase of Al content, the strength and elongation first increase and then decrease.