The invention provides a method for forming a functional layer on a porous metal base material, which comprises the following steps of: putting the porous metal base material into high-temperature resistant penetrating agent powder consisting of metal powder, filling agent and energizer, and thermally treating the porous metal base material for certain time at the temperature of between 900 and 1,200 DEG C. The metal powder consists of one or more of Cr, Al, Mn, Co, Mo, Ti, W, V and Re; the filling agent is selected from one or more of aluminum oxide, silicon oxide, silicon carbide, zirconium oxide, boron nitride and ceramic powder; and the energizer is ammonium halide. A hot penetration process for the metal powder is successfully applied to the porous metal material, and certain applicable process conditions are found; an alloy coating with a good protective film is formed on the porous metal base material by the method; and in addition, the method is a dry process, does not produce waste water or waste gas, basically does not pollute the environment, and has excellent environmentally-friendly performance.