Polystyrene-divinylbenzene-based Amberlite XAD-2 was functionalized with ortho-vaniilinthiosemicarbazone and its analytical properties were investigated. The resin was used successfully for the separation and preconcentration of thorium(IV) and uranium(VI) ions prior to their determination by spectrophotometry and by ICAP-AES and GF-AAS, respectively. The influence of several ions as interferents is discussed. The resin exhibits good chemical stability, reuseability, and a faster rate of equilibration for their determination. The proposed method has been applied to sequential chromatographic separation of thorium(IV) and uranium(VI) on river water samples with good analytical reliability such as recovery of 97-98%, relative standard deviation of 2-3%, and a detection limit of 100 ng.mL(-1). The present method is also used for their determination in monazite sand and some standard geological materials.