FIELD: physics. SUBSTANCE: invention relates to an alpha-spectrometric method of determining uranium isotope composition in sulphuric acid process solutions, involving uranium pre-separation from a sample, preparing a counting sample by electrolytic deposition of uranium on a substrate from corrosion-resistant steel, calibrating the alpha-spectrometer based on the energy of the detected alpha particles, measuring the alpha-radiation spectrum of the obtained countable sample, calculating the areas of uranium isotope alpha-radiation peaks at predetermined energy intervals, wherein preliminary extraction of uranium from sample is carried out directly from sulphuric process solution by sorption on anionite with pyridine groups with subsequent desorption of uranium by uranium desorption solution containing sodium nitrate (NaNO3) and sulphuric acid (H2SO4). EFFECT: disclosed is an alpha-spectrometric method of determining uranium isotope composition in sulphuric acid solutions. 1 cl, 2 dwg, 3 tbl, 4 ex.