Uranyl compounds exhibit characteristic optical properties in absorption and emission,which has been utilized to study speciation of uranyl in natural and artificial environments.[1] Theoretical explorations of the coordination structure,electronic structure and excited states of uranyl compounds are essential to understand the nature of the excited states and luminescence spectra.[2-4] In this work,we have studied the electronic absorption and emission spectra of free UO2F2 and its water solvated complexes below 32,000 cm-1 at the levels of ab initio CASPT2 and CCSD(T)with inclusion of scalar relativistic and spin-orbit coupling effects.The influence of the water coordination on the electronic spectra of UO2F2 is explored by investigating the excited states of solvated complexes(H2O)nUO2F2(n = 1-3).In these uranyl complexes,water coordination is found to have appreciable influence on the 3△(Ω = 1g)character of the luminescent state and on the electronic spectral shape.The simulated luminescence spectral curves based on the calculated spectral parameters of(H2O)nUO2F2 from CCSD(T)approach agree well with experimental spectra in aqueous solution at both near liquid helium temperature and room temperature.The possible luminescence spectra of free UO2F2 in gas phase are also predicted.Our study shows that combination of theory and experiment can provide an in-depth understanding of the excited states and luminescence property of uranyl systems.