234U/238U activity ratios in geological reference materials are determined using α-spectrometry after a simple chemical separation procedure. This procedure includes a single anion exchange (SO4-form resin) and uranium can be separated from thorium and other heavy metal cation. Although the activity ratios of most samples are nearly unity, those of the samples which suffered secondary geological processes such as metasomatism (GnA, GXR-1), sedimentation (SO-1, TS) and weathering, showed radioactive disequilibrium. So, it is important to pay much attention to the nature of the sample in these case for conventional γ-spectrometry. Uranium contents determined by fluorimetry are in good agreement with the reference values, and a good correlation between counting rates of238U and uranium contents is recognized.