The invention relates to a
flame-retardant
fiber board and a manufacturing method thereof. The
flame-retardant
fiber board is prepared from the following raw materials in portion by weight: 80 to 120 portions of
fiber, 80 to 120 portions of magnesia, 80 to 200 portions of water solution of
magnesium sulfate, 5 to 30 portions of active silica, 0.5 to 2 portions of
organosilicon waterproof agent, and 0.5 to 1.5 portions of
plasticizer. The manufacturing method comprises the steps: 1) preparing the fiber, namely cleaning and
drying crop straws, wood branches or
wood processing residual materials, and then obtaining the fiber through the crushing by a crushing
machine; 2) preparing an inorganic
adhesive, namely mixing the magnesia, the water solution of the
magnesium sulfate, the active silica, the
organosilicon waterproof agent and the
plasticizer, and stirring the mixture to obtain the inorganic
adhesive; 3) mixing the fiber and the inorganic
adhesive prepared through the step 1 and the step 2, stirring the mixture, and paving the mixture after the screening by a screening
machine; 4) paving a reinforcing
network on the upper and lower surfaces of a paved slab; and 5) finally performing
hot pressing on the board paved with the reinforcing network for 10 to 25 minutes at a temperature of between 100 and 110 DEG C at a pressure of between 12 and 30MPa to obtain the
flame-retardant fiber board. The flame-retardant fiber board has broad application field.