Abstract: The research of new uranium-based compounds is of great significance for the development of new high-efficiency nuclear fuel rod assemblies and the promotion of depleted uranium resource utilization. Compared with uranium oxide compounds, of which the crystal structures and physical and chemical properties of inorganic uranium oxides have been extensively studied, the current research on uranium fluoride is still relatively scarce, despite UF₆ being a common substance in uranium enrichment. This has sparked our great interest in the synthesis and physical and chemical properties of uranium fluorides. Additionally, there is controversy about the synthesis of uranium fluoride. Some reports claim that uranyl acetate and Cu salt catalysts are key to the synthesis, but this has been questioned. More work on the synthesis conditions for uranium fluorides are desirable to clarify these disputes. In this work, to enhance the understanding of the product types and synthesis conditions of ternary uranium fluorides, we employed a synthesis strategy involving in-situ reduction of uranyl nitrate by methanol under hydrothermal conditions and coordination with cesium fluoride without the use of catalysts to synthesize three new ternary uranium fluorides with cesium as the alkali metal: CsU₃F₁₃, Cs₂U₂F₁₀, and Cs₂U₄F₁₈. Single crystal X-ray diffraction confirmed that the U⁴⁺ in all three compounds form nine-coordinate environments with fluorine atoms, presenting complex three-dimensional or two-dimensional structures with U(Ⅳ) as the metal node. Due to the scarcity of characterization of the physical and chemical properties of fluorides, the optical properties, thermodynamic behaviors, and magnetic behaviors of the three compounds were studied. The UV-visible spectra of the three compounds exhibit typical U(Ⅳ) characteristic bands, with band gaps of 3.55, 4.13, and 4.23 eV, respectively. The structures of all three compounds can be maintained stable at 120°C under a nitrogen atmosphere. The three compounds are paramagnetic, with effective magnetic moments of 1.82, 2.77, and 2.40 μ_B/U. The nonlinear relationship between magnetization and temperature in the low-temperature region indicates a singlet state of U(Ⅳ) at low temperatures. All magnetic behaviors are consistent with the characteristics of U(Ⅳ). Theoretical band gaps, lattice energies, and formation enthalpies of the three compounds were calculated using density functional theory. The formation enthalpies of the three compounds are −3.619, −3.560, and −3.455 eV/atom, and the lattice energies are 5.587, 5.307, and 5.285 eV/atom, respectively. Based on the formation enthalpies and lattice energies, CsU₃F₁₃ is determined to be the most stable compound due to its higher crystal symmetry and three-dimensional framework structure. This work enriches the existing uranium fluoride database, provides detailed physical and chemical properties, and offers insights into the synthesis of novel ternary uranium fluorides.