The invention relates to a ferritic steel plate with a nanaoscale spherical cementite enhancing function and a preparation method of the ferritic steel plate. The steel plate is prepared from, by mass percent, 0.95%-1.05% of Cr, 0.95%-1.00% of Mo, 0.68%-0.75% of Mn, 0.57%-0.62% of Ni, 0.37%-0.52% of Al, 0.39%-0.45% of C and the balance Fe and inevitable impurities. The microstructure of the ferritic steel plate is equiaxed ferritic grains, nanaoscale spherical cementite is dispersed and distributed in the ferritic grain boundary region, the diameter of the grains ranges from 0.4 micrometer to 3 micrometers, and the size of the nanaoscale spherical cementite ranges from 70 nm to 150 nm; and the thickness of the ferritic steel plate ranges from 1.4 mm to 2.0 mm. The preparation method comprises the steps that 1, smelting is carried out under gas shield; 2, hot rolling is carried out after solid solution treatment; 3, warm rolling is carried out after heat treatment; and 4, annealing is carried out to obtain the finished steel plate. According to the steel plate, the yield strength and tensile strength of the steel plate are improved, and the good machining performance and plastic deformation capacity are achieved. The preparation method is simple, and industrial production can be achieved.