The invention discloses nanometer / ultrafine crystal structure ultrahigh-strength plasticity austenitic stainless steel and a preparation method, and belongs to the field of ultrahigh-strength plasticity alloy steel production. Raw materials comprise the following chemical components: 0.08-0.15% of C, 0.35-0.75% of Si, 7.5-10% of Mn, 0.5-0.9% of Cu, 1-1.5% of Ni, 14-16% of Cr, 0.1-0.25% of N, P notmore than 0.06%, S not more than 0.03%, and the balance of iron and inevitable impurities. After smelting by a vacuum induction furnace, a casting blank is forged, and a forging is hot rolled; twicecold rolling annealing is performed after the solid solution treatment; a nanometer / ultrafine crystal composite structure is obtained by using reversion of strain induction martensite and recrystallization of deformation austenite. The ultrahigh-strength plasticity of stainless steel is realized through fine crystal strengthening, back stress reinforcement, deformation induction twins effect and deformation induction martensite effect. The prepared stainless steel is prominent in comprehensive mechanical performance; the yield strength reaches 1150-1320 MPa, and is 3.2-4.5 times in an originalsolid solution state; the tensile strength reaches 1350-1440 MPa; the ductility still achieves a higher level of 39.2-47.3%; the cost is lower; and the preparation method is simple and feasible.