The invention concerns a method for oxidising a textile mass, in particular woollen, to modify the surface of the fibres whereof it is formed, essentially consisting in: a) transforming said textile mass into a textile mass containing 12.5 to 60 % (g/g) of water and having a structure such that a gas can pass through it uniformly and thoroughly; and b) passing through said mass, for 5 to 20 minutes at room temperature, a gas mixture containing 20 to 150 g of ozone per m3, which is continuously injected through said mass while it moves along on a carrier system, being alternately directed on both surfaces of said pass. Said treatment is preferably carried out in a sealed chamber, the ozone being destroyed in output.