The anion exchange behavior of a negatively charged complex of thorium is studied on Dowex-21 K. Various eluants were tried. Hydrochloric, sulfuric, and nitric acid, as well as chlorides, nitrates, and acetates of sodium and ammonium, were tested as eluants. The efficiency of various eluants was determined. Novel methods were developed for the separation of thorium from a large number of elements by the processes of selective sorption, selective elution, and gradient elution. The method was found to be applicable for the separation of thorium from fission product elements.