The structures of hybrid two-dimensional (2D) Ruddlesden-Popper (RP) phase-layered halide perovskite (BA)2CsPb2Br7 in the temperature range of 100 to 450 K were constructed and systematically investigated by first-principles calculations. The results showed that the perovskite materials were thermodynamically stable and exhibited the properties of direct band gap semiconductors in the temperature range of 100 to 400 K. However, a first-order phase transition occurred when the temperature was raised to 450 K, causing transformation of the orthorhombic to tetragonal space group. The absorption spectra and transition dipole moments of (BA)2CsPb2Br7 were discussed at the temperature range of 300 to 450 K. A large dipole transition matrix element P2 is observed at 300 K, which implies that the emissive property of the 2D RP phase-layered perovskite (BA)2CsPb2Br7 is less affected by thermal quenching at room temperature. This highlights the potential of 2D layered halide perovskites for large-area and low-cost light-emitting diodes.