The invention relates to a high-toughness microalloyed Al-containing medium manganese hot rolled steel plate and a preparation method thereof and belongs to the technical field of a new generation of a steel plate for an automobile. The key point is that a retained austenite phase at a certain volume fraction is obtained by means of reasonable chemical components and process, so that grain size control and distribution of alloy elements are realized. The high-toughness microalloyed Al-containing medium manganese hot rolled steel plate comprises the components in percentages by mass: 0.15-0.2% of C, 7.6-8% of Mn, 5.4-6% of Al, 0.01-0.02% of Si, 0.02-0.04% of Nb and the balance of Fe and inevitable impurities. The preparation method comprises the following steps of: preparing a steel blank according to component proportion; heating and insulating the steel blank and performing hot-rolling to obtain the hot rolled steel plate; air-cooling the hot rolled steel plate to room temperature; and performing post-rolling thermal treatment to obtain the high-toughness microalloyed Al-containing medium manganese hot rolled steel plate, wherein the density is 6.85-6.99g/cm<3>, the tensile strength is 940-1250MPa, the ductility is 20-40%, and the product of strength and elongation is 30GP% or above.