Abstract: Uranium-containing wastewater from the spent nuclear fuel are radioactive wastes as well as energy sources. It is meaningful to investigate the configurations of aqueous U（Ⅵ） for its environmental migrations and configuration conversions. Herein the uranyl complexes of \left\mathrmUO_2(\mathrmOH)_m(\mathrmH_2\mathrmO)_n^ \right^2-m (m=1-4, n=1-2) were investigated by density functional theory at the PBE0 level, in combination with ECP80MWB_AVQZ + 2f basis set for uranium and 6-311+G** basis set for hydrogen and oxygen. The optimized geometries, energies, formation processes and thermodynamic properties of the complexes were predicted. In the six coordinated complexes that are spontaneously produced, the ligand numbers of OH^‒ and H₂O are 4 and 2, respectively. There exist either linear or “V” configurations, sorting by the angles of O_yl-U-O_yl, when a linear uranyl dication coordinated with H₂O and hydroxyl. The “V” type complexes with O_yl-U-O_yl angle being about 40° are found only when the coordinated number of OH^‒ is more than 2. The total energy of “V” type UO₂(OH)₃^‒ is lower than that of its linear isomer by 131.46 kJ/mol at the MP2 level. The complexes with U-OH₂ bond and “V” type O_yl-U-O_yl are the most stable. The complexes tend to have a “V” configuration when the coordinated hydroxyl number is 3 or 4. The lengths of U-O_yl bond increase as the angles of O_yl-U-O_yl decrease. The complexes tend to be cage-like as more hydroxyl and H₂O are coordinated. When \mathrmUO_2^2+ coordinates with OH^‒ one by one, a large amount of energy is released initially. As the coordinated number increases, the released energy dramatically decreases or even changes to an energy adsorbing process. When \mathrmUO_2^2+ coordinates with H₂O one by one, the processes release a small amount of energy continuously. The increase of H₂O ligand is beneficial to the stability of the complexes. The formations of UO₂(OH)_m^2‒m (m＜4) are spontaneous processes. However, for the formation of UO₂(OH)₄^2‒, only the process of linear UO₂(OH)₃^‒ converting to “V” type UO₂(OH)₄^2‒ is spontaneous, indicating the complexes tend to form “V” configuration when the number of OH^‒ is 4. The spontaneous pathways and energy changes in the stepwise coordination processes were speculated on the basis of energy analysis. The above characteristics of UO₂(OH)_m(H₂O)_n^2‒m play an important role on the ion activity, solubility and ion exchange of uranyl in alkaline solutions. OH^‒ and H₂O compete with each other in coordinating, which influences the concentration and species distribution of UO₂(OH)_m(H₂O)_n^2‒m configurations. The results herein provide theoretical basis for understanding and controlling the behaviors and reactions of uranyl aqueous solutions.