Abstract: A method for the determination of uranium and thorium in nuclear wastewater by total reflection X-ray fluorescence spectrometry(TXRF) with direct sample preparation was established. Ga was used as an internal standard, the detection limits for U, Th are 0.010, 0.008 mg/L, and the relative standard deviation of the standard solution measurement is less than 7%(n=6), and the marked recovery is between 95% and 115%. The method has been applied to the determination of unknown samples, and the results are in good agreement with ICP-MS. The slope of equation of line regression about U and Th is 0.93 and 1.0 respectively. The correlation coefficient of equation about U and Th is 0.997 and 0.999 respectively.