Inorganic perovskite nanostructures have attracted considerable attention for their tunable band gaps and excellent optoelectronic properties. It is inevitable that phase segregation of halide perovskite usually occurs in mixed-halide perovskites under a focused laser illumination, which caused by photo-induced halide-ion segregation. Here, we reported an uniform perovskite alloy nanowires via a chemical vapor deposition (CVD) method. Microstructural characterization reveals that these perovskite nanowires have independent linear morphology with high-quality crystalline. Micro-photoluminescence (PL) spectra exhibit that these nanowire structures show a dual-wavelength emissions at 690 and 570 nm, respectively. Additionally, time-dependent PL intensity of the emission peak at 690 nm is increased by the decrease of the emission peak at 570 nm under a focused laser illumination, indicating the formation of phase segregation at the excited positions. Moreover, based on these as-grown halide perovskite CsPbBr_2.52I_0.48 nanowires, a reasonably optical switch is designed and constructed. This optical switch may have potential applications in timed blasting system and time-delay circuit in the future.