The invention provides a flame-retardance formaldehyde-free industrial hemp straw fiberboard. The fiberboard comprises raw materials of industrial hemp straw all-straw core fragments and flame-retardance adhesive being 18-48 weight% of the fragments; and the fiberboard is prepared by such steps as cold pressing and curing. Aiming at a hot pressing process and a method for applying solvent adhesive in traditional fiberboard manufacturing, the flame-retardance formaldehyde-free industrial hemp straw fiberboard is prepared by using a cold pressing process and special flame-retardance formaldehyde-free adhesive. Compared with a traditional fiberboard preparation method, the method has the advantages of simple process, low energy consumption and no environmental pollution; and compared a wood fiberboard, the obtained product has such characteristics as flame retardance, low smoke, no irritation, no poison, no formaldehyde, bacteria resistance, insect resistance, water resistance, high strength and possession of both medium density and high density.