Poly 3-aminopropyltriethoxysilane is a highly reactive high-molecular polymer because of the existence of abundant amino groups, which presents a strong affinity toward different metal cations. In view of this, the novel poly amino siloxane oligomer modified graphene oxide composite (PAS-GO) was fabricated by a facile cross-linking reaction and applied to capture U(VI)/Eu(III) ions from aqueous solution. The interaction mechanisms between the PAS-GO and U(VI)/Eu(III) were elaborated. The modification by NH2 increased the sorption sites and improved the sorption capacities because of the synergistic effect of chelation with U(VI)/Eu(III). X-ray photoelectron spectroscopy revealed that nitrogen groups are involved in the removal of U(VI)/Eu(III) since nitrogen atoms of amine groups provided the lone pair of electrons with U(VI)/Eu(III) species. The maximum sorption capacity of U(VI) and Eu(III) on the PAS-GO at 298 K calculated by the Langmuir isotherm model was 310.63 and 243.90 mg/g, respectively. The PAS-GO could be repeatedly used for more than five cycles with slight degradation of sorption. High sorption efficiency and excellent reusability make the PAS-GO composite an ideal candidate for the capture of U(VI)/Eu(III) from aqueous solution.