The invention relates to a method for the treatment of silicon carbide fibers, comprising a step involving the chemical treatment of fibers with an aqueous acid solution containing hydrofluoric acid and nitric acid but free of acetic acid in order to remove the silica present on the surface of fibers and to form a layer of microporous carbon. The invention also relates to a method for the production of a fibrous preform, comprising the formation of a fibrous structure comprising treated silicon carbon fibers and the use of said preform for the production of a part made from composite material.