The invention relates to the technical field of automobile steel, in particular to a method for manufacturing a cold-rolled medium manganese steel plate with high strength and plasticity and free of yield platform. The manufacturing method mainly comprises the following steps of (1) smelting and forging; (2) full-austenitizing rolling, wherein a steel blank is heated to 1100-1200 DEG C, heat preservation is carried out for 2-3 hours, then full-austenitizing rolling is carried out, the steel blank is rolled to 4-5mm thick, and the steel blank is naturally cooled to room temperature; (3) pre-annealing before cold rolling, wherein the steel plate subjected to hot rolling is heated to 640-650 DEG C in a two-phase-region along with a furnace, heat preservation is carried out for 6-8 hours, thenthe steel plate is cooled to 200-300 DEG C along with the furnace, and then the steel plate is air cooled to the room temperature; (4) cold rolling, wherein the steel plate subjected to hot rolling and annealing is rolled to 1-2mm thick by a cold rolling machine; and (5) two-step heat treatment after cold rolling, wherein the purpose is to change the structure and the shape of the steel plate, the shape of the steel plate is changed into a strip shape from an isometric shape, and the structure of the steel plate is composed of ferrite and austenite. According to the manufacturing method, thesteel plate with high strength and plasticity is obtained, meanwhile, the stress-strain curve is continuously yield, and the common yield platform phenomenon in cold-rolled manganese steel is eliminated.