Abstract: The condition of quantitative adsorption of 10~(-3) ppm level U and Th in wa-ter by sulfate form D235 and hydrogen form DO33 macroporous ion-exchangeresin is studied. The U and Th are adsorpted and then eluted with water and 8%(NH_4)_2CO_3-0.2K NH_3.H_2O solution respectively. Non self-adsorptive U, Th α-sources are prepared by constant current electrodeposition. The a activety of sour-ces are determinated with α-ray spectrometer. The method is used to determine10~(-3) ppm level U, Th and ~(234)U/~(238)U,~(230)Th/~(232)Th in water with precision of±10%and±7% for U~(234)U/~(238)U and~(230)Th/~(232)Th respectively.