The separation of lithium and sodium with a local made canon exchange resin (Sine No.1, nuclear sulfonic acid type) is investigated. The column (16×500 mm) is filled with 40 g (dry basis) of the resin (80-120 mesh). For lithium-sodium mixtures (total alkalies, 10 meq in 100 ml of solutions) with less than 2.5 meq of lithium can be separated quantitatively from sodium. Eluent used is a mixture of 0.2 N hydrochloric acid and methanol(7:3 by volume).The optimum rate flow is found to be 1.8-2.1 ml/min. The separation takes about four hours.