<p>This study investigates the feasibility of manufacturing large 316H austenitic stainless steel forgings using metal additive forging technology, through a series of experiments. Through hot compression bonding experiments, a peak stress-based constitutive equation for hot deformation and a high-temperature constitutive equation based on the strain compensation method were established. By constructing hot processing maps, the optimal processing window for the 316H stainless steel hot compression bonding experiment was identified. By analyzing the evolution of the interface under different deformation temperatures, strains, strain rates, and holding times, the interface bonding ratio was used to quantitatively assess the degree of bonding. The best process parameters for interfacial bonding were obtained. Based on this, optimal theoretical process parameters were applied in isothermal closed-die forging experiments, resulting in the production of a multilayer additive forging billet of 316H stainless steel. Mechanical property testing of the billets showed that the samples manufactured using the metal additive forging technology exhibited good plasticity, with a yield strength of approximately 250 MPa, a tensile strength of approximately 575 MPa, and an elongation exceeding 73.96%, which exceeds those of the base material and thereby demonstrating the process feasibility. Fracture analysis revealed that the fracture mechanism of the multilayer additive forging billets sample was predominantly ductile fracture, whereas the fracture mechanism of the 316H base material sample was ductile-brittle mixed fracture.</p>