Abstract: In this paper uranyl sulphate species adsorbed on quaternary ammonium resin are studied with infrared spectrometry. It has been found that when UO2 (SO4) 22- or UO2 (SO4) 34- is adsorbed the asymmetric stretch of UO22+, v3, is observed at 918 cm-1 or 910 cm-1 respectively. When the resin is brought io equilibrium with the solution similar to that used in uranium hydro-metallurgy, the value of n in the complex UO2(SO4)n2-2n is 2.5-2.7, v3 of UO22+ and the peak assigned to quaternary ammonium group of the resin are merged at 900 cm-1 After the loaded resin is pressed into disks with KBr, exchange reaction takes place, thus uranyl sulphate complexes turn to UO2(SO4)22- and SO42. According to the amount of U and SO42- on loaded resin found from chemical equivalent method and the final free SO42- determined by IR, the value of n is calculated.