The invention discloses a four-in-one method for corrosion-preventing, inflaming-retarding, hardening and air purification of wood. The four-in-one method comprises the following steps: sufficiently mixing water, disodium octaborate tetrahydrate, aluminum dihydrogen tripolyphosphate, boric acid and magnesium sulfate, dissolving for preparing a combined solution, and preparing wood to be treated, wherein the weight percentages of the chemicals in the combined solution are as follows in sequence: 12.5%-15%, 5-6%, 5-6%, and 2.5-3%; placing the wood to be treated into an airtight container, adding the combined solution, and heating to 120-132 DEG C, wherein the pressure is kept at 0.2-0.3Mpa for 16-28 hours. By virtue of the four-in-one method provided by the technical scheme of the invention, the special combined solution is used for dissolving for removing most grease and sediments in the wood, so that a plurality of tiny pipe holes axially communicated are formed inside the wood, meanwhile, exchange filing is realized in the pipe holes of the wood, so that the purposes of preventing corrosion, retarding inflaming, hardening and air purification treatment of the wood are realized, energy conservation and environment protection are facilitated, and industrial prospect is good.