The invention belongs to the field of marine chemical industry medicine intermediates, and particularly relates to a method for preparing pyrogallol and phloroglucinol, wherein the preparation route that trimethoxybenzaldehyde is subjected to catalysis decarbonylation under a hydrogen atmosphere is adopted, the modified raney nickel is adopted as a catalyst to carry out a catalysis decarbonylation reaction in a solvent, the modified raney nickel is subjected to bulk phase and surface modification based on the conventional raney nickel preparation method, the modified component is one or a plurality of materials selected from Mn, Fe, Cr, Mo, Ti and W, and the modified component content (wt) is 0.5-10 wt%. The method has characteristics of environmental protection, easy operation, wide raw material source, short reaction step, simple catalyst preparation and capability of being repeatedly applied multiple times, and is suitable for industrialization.