A method of manufacture of medium and high density fibreboard with moisture and mildew resistance and low formaldehyde emission, which includes the steps of: (a) providing wood chips; (b) pre-steaming; (c) refining the wood chips into fibers and adding 200-230 kg/m3 urea-formaldehyde resin adhesive, nigrosine solution with a mass percentage of nigrosine in absolutely dried fiber of 1-1.2%, 6-8 kg/m3 refined paraffin and 1.5-2 kg/m3 curing agent; (d) feeding activated carbon of 100-200 mesh to mix with the fibers and then drying the fibers to a water content between 8-10%; (e) separating qualified fibers to measuring silo; (f) laying the fibers onto a mat formation platform uniformly to form a fiber mat by pre-pressing; (g) pre-heating the fiber mat; and (h) processing continuous hot-pressing to form a raw board. The resulting fiberboard is black in color, has good physical properties and low formaldehyde emission rate.