The invention discloses a high-toughness polypropylene foamed plate for externally packaging a steel coil and a preparation method thereof. With the advantages of light mass, low price, high toughness and good properties of enduring folding, temperature as well as weather, the foamed plate can be used as a circumferential protection plate, an end-face protection plate and a corner protection plate for the steel coil. The high-toughness polypropylene foamed plate for externally packaging the steel coil is made from the following raw materials (the weight percent of each raw material is shown in brackets): polypropylene resin particles (60 to 70%), polypropylene resin powder (25 to 35%), a polyfunctional monomer (1 to 6%), nano powder catalyst (0.5 to 3%), an accelerating agent (0.01 to 0.2%), an initiating agent (0.05 to 0.5%), an antioxidant (0.2 to 2%), a wetting dispersant (0.1 to 0.3%), a foaming agent (0.5 to 2 %), and a master batch (0 to 3%), wherein the polyfunctional monomer is trimethylolpropane triacrylate or trimethylolpropane trimethylacrylate.