As the first family of Sn-based alkaline earth metal mixed halides, three new compounds, BaSn2F5X (X = CI, Br, and I), are synthesized by hydrothermal method. These compounds are crystallized in the centrosyrnmetric space groups of P2(1)/c, P4/nmm, and Pmma for BaSn2F5CI, BaSn2F5Br, and BaSn2F5I, respectively; and their microscopic frameworks are all composed of the fundamental structural unit [SnF4](2-)and its derivatives ([SnF4Cl](3-) and [SnF5](3-) groups). Interestingly, the structures in BaSn2F5X are significantly changed from one-dimensional (1D) to two-dimensional (2D) and then to 1D motifs as X varies from CI, Br, to I. Structural analysis combined with theoretical calculations reveals that the structural diversities are caused by the difference of ionic radius and electronegativity of X- anions as well as the orientation of the lone-pair electrons on Sn2+ cations. Moreover, the optical, electronic, and thermal properties for these three compounds are determined. This work provides a representative example to show how microscopic ions influence the structures, thus in favor of the design for new mixed halides, a type of important functional materials with many optoelectronic applications.