A simple source preparation method was developed for α-ray spectrometry to determine U and Th isotopes in silicate rock samples. Samples were decomposed by the mixed acid of HF-HCIO4-HNO3, and U and Th was isolated by use of UTEVA Spec. resin. Isolated U and Th were then extracted into TTA-benzene solution for purification. The organic phase was evaporated on a hot stainless steel planchet to dryness. This method is effective for the speedy preparation of thin sources of U and Th for α-ray spectrometry.