The invention discloses a fiber reinforced magnesium oxychloride red mud plate and a preparation method, and belongs to the utilization technology of waste material-red mud produced in alumina industry. The plate mainly comprises a solid blending material and brine, wherein the weight ratio of the brine is 15-30%, and the solid blending material comprises the following components by weight ratio: 30-70% of red mud, MgO of 25-60 % and 5-10% of reinforcing fiber; and 0.5-5% of modifier is added into the brine. The wet red mud, the magnesium oxide, the reinforcing fiber and the brine added with the modifier are subjected to extrusion molding by roller pressure after being uniformly mixed, naturally harden after solidification, and form a standard material or profile after shear processing. The plate is of a high-strength solidification plate with high content of red mud, has the advantages of fireproof, waterproof and anti-static performances, heat and noise insulation, strong pressure resistance, good fracture resistance, good corrosion resistance and the like, is widely used in construction, decoration and other industries, and can digest a lot of red mud to truly turn waste into wealth.