The present invention relates to a method for preparing a highly pure trifluoromethanesulphinic acid. The method of the invention for preparing a highly pure trifluoromethanesulphinic acid, starting from an aqueous mixture comprising a trifluoromethanesulphinic acid salt, a trifluoroacetic acid salt and saline impurities resulting from the method for preparing same, is characterized in that said mixture is subjected to the following operations: - acidification such that the trifluoroacetic acid salt and the triflinic acid salt are released in an acid form, - separation of the trifluoroacetic acid and trifluoromethanesulphinic acid by distillation enabling the trifluoroacetic acid to be recovered at the top of the distillation and the trifluoromethanesulphinic acid to be recovered at the bottom of the distillation, - separation by distillation of the trifluoromethanesulphinic acid present in the distillation residue previously obtained.