The invention belongs to the technical field of heat treatment of materials, and in particular relates to a low-carbon, medium-manganese, high-residue, high-strength and tough steel and a heat treatment method thereof. The mass percentage ratio of the chemical composition of the steel is: C: 0.10-0.25%, Mn: 4.0-8.0%, Al: 1.0-2.5%, and the balance is Fe and other unavoidable impurities. In this method, after the steel smelting, continuous casting, hot rolling and other processes, the hot-rolled steel plate is subjected to the following heat treatment: low temperature tempering-cold rolling-rapid heating-two-phase zone isothermal for a very short time-rapid cooling. The average grain size of retained austenite in the final high-strength steel is less than 200nm, the volume fraction can reach 15%-40%, and the matrix is a heterogeneous structure of equiaxed recrystallized ferrite + strip unrecrystallized ferrite; The yield strength is in the range of 800MPa‑1200MPa, the tensile strength is in the range of 1200MPa‑1500MPa, and the uniform elongation can be achieved at 10%‑20%. The invention obtains excellent mechanical properties and realizes high-efficiency heat treatment at the same time by improving the morphology of the ferrite matrix and the volume fraction and grain size of the retained austenite.