The invention relates to a stainless steel material and a preparation method thereof. The stainless steel material comprises the following components of, by mass percentage, 16-25% of Cr, 12-17% of Mn, less than 0.25% of C, less than 1% of Si, 0.3-0.9% of N, and the balance Fe and unavoidable impurities; the stainless steel material is nickel-free, multilayer and biphase stainless steel; the surface layer of the stainless steel is an austenite structure; and the core of the stainless steel is an austenite-ferrite biphase structure. The provided stainless steel material can be subjected to 24 hsalt mist and 24 h artificial sweat instead of being corroded, does not contain nickel and molybdenum, does not have the nickel allergy risk, is lower in raw material cost, and has the obvious advantages in aspects such as the magnetic property, simplification of a machining technology, and less material removal in the part machining process.