The invention belongs to the technical field of building materials and particularly relates to a plant-fiber external wall panel with wood-like grain. The external wall panel comprises an upper material layer, a middle material layer and a lower material layer, wherein the upper material layer and the lower material layer are both prepared from the following raw materials: sulphoaluminate cement,water, plant fiber and additives; the middle material layer is prepared from the following raw materials: sulphoaluminate cement, water, the plant fiber and additives; glass fiber mesh cloth are laidin the upper material layer, a middle material layer and a lower material layer; wood grain is arranged on the outer side of the upper material layer. Besides, the invention also provides a method forpreparing the external wall panel. The plant-fiber external wall panel with the wood-like grain has low density and high toughness; the external wall panel has the wood grain at the product preparation stage, and the extra cost of late decoration is reduced. The adopted raw materials are cheap and easily available, so that the production cost of the product is reduced.