Dimethylheptyl methylphosphonate (P350) was used as a stationary phase for concentrating uranium and thorium. The behaviour of Kel-F, silica gel etc as supporter were tested. A solution containing 15 % HN03, 15 % NH4N03 [or 7 0 % Al (N03) 3] and 2 % tartaric acid of U and Th is used for column sorption. Th and U were separated by elution of 5N HCl and 0.2% NaF respectively. The chromatographic column could be used more than 80 times.