Abstract: A new extraction-chromatographic separation of indium (Ⅱ) from coexisted ions has been introduced. The di(1-methylheptyl) methylphosphonate (P350) resin is used as a stationary phase clear-cut separation is evidenced by the blank eluates in between the elution peaks of indium (Ⅲ) and its neighbouring ions,so that it can be used in the determination of indium. In the presence of suitable surfactant (such as CTMAB etc) the collected eluate of indium (I) is coloured with suitable chromogenic reagent (such as salicylfluorone etc), and then the indium may be determined spectrophetometrically. From the determined data of indium in some synthetic solutions and actual samples, it has been proved that this procedure is suitably used to determine microamount of indium with high accuracy and reproducibility.