The invention belongs to the field of metal materials, and relates to a novel high strength steel board low in density, high in strength and good in anti-corrosion performance, in particular to component design and a preparation method of the novel automobile-used steel. The automobile-used steel board is characterized by comprising the following specific chemical compositions by mass percentage: 0.60-0.70 percent of C, 0.30-0.40 percent of Si, 10.0-15.0 percent of Mn, 5.0-10.0 percent of Al, less than 0.005 percent of P, less than 0.003 percent of S and Fe and unavoidable impurities in balancing amount. The preparation process comprises the following steps: performing smelting according to the chemical compositions, and forging casting blank material into a steel blank; heating the steel blank to 1,130-1,170 DEG C, keeping the temperature for 2 hours, and performing multi-pass hot-rolling deformation, wherein the rolling starting temperature ranges from 1,030-1,070 DEG C, the rolling stopping temperature ranges from 850-900 DEG C, the accumulated deformation amount ranges from 80 percent to 85 percent, and the rolling temperature is from 200 DEG C to 250 DEG C; after hot rolling, further performing solution treatment of the steel board, keeping the temperature at 1,000-1,050 DEG C for 0.5-1 hour, and performing water quenching treatment; taking a dual-phase organization combining austenite and ferrite, and obtaining the lower density and high toughness automobile-used steel board.