The invention discloses a mortar caul plate formed by a stacking glass fiber felt and a glass fiber net. At present, building external wall decoration materials mainly include external wall coating, external wall bricks, stones, a glass curtain wall and the like and have different advantages and disadvantages. According to the mortar caul plate, the glass fiber felt and the glass fiber net are stacked and are wrapped by composite grout formed by emulsion, cement, quartz powder, dispersing agents, early strength agents, water-retaining agents, antifoaming agents and water, and the mortar caul plate is obtained after drying. The mortar caul plate has the advantages of being soft, light, thin, anti-cracking, anti-folding, anti-aging, resistant to moisture, environmentally friendly, safe, low in production cost, easy to construct and low in construction cost, saving energy and the like; the motor caul plate overcomes the defects that existing external wall decoration plates are large in self-weight, high in construction cost, high in manufacturing cost and the like.