Extraction of uranium from nuclear wastes is of great significance, and nowadays has attracted much attention. In the present work, the thermodynamics, complex geometries and coordination mode of UO2(NO3)(2) with N-methyl-N-decyl-octanamide and its amides in aqueous solutions were investigated detailedly with M06-2X method. This theoretical model reveals that: 1) In UO2(NO3)(2), there is a strong ionic interaction between the two NO3 ligands; 2) For the complexes of UO2(NO3)(2) with amides, the ligands coordinate to the vacancy of UO2(NO3)(2) via the mono-dentate mode; 3) The hydrophobic interactions compete with the steric effect, and the most stable complexes bear hydrophobic interactions between the parallel long-chain alkyl groups; 4) Long substituent and strong hydrophobic interactions help extraction of uranium(VI) from aqueous nitric acid solutions. (C) 2017 Elsevier Ltd.