Gamma absorptiometric method was used to determined uranium and thorium concentration in both aqueous and organic solutions. The complete computer-based γ-spectroscopy system includes a coaxial Ge(Li) detector used to measure the absorption of γ-rays from 241Am through the solutions. The absolute concentration of natural uranium and thorium can be determined within 1–200 g U/L and 1–360 g Th/L concentration ranges with a precision of ± 1% for a counting time of up to 100 s with the result that the method is suitable for on-line measurement in fuel element fabrications.