In addition to amplitude, frequency and phase, the polarization states of light can also carry information and thus will find important applications in imaging, medical detection and optical communication. Traditionally, the generation and detection of polarized light mainly rely on the combination of commercial unpolarized light sources and photodetectors with polarizer and wave plate, which are usually bulky and costly. Therefore, it is urgent to develop alternative strategies to achieve on-chip compact polarized light source and detector. Optical anisotropy is related to the polarization response of optoelectronic devices, which is the basis for polarization optical elements such as polarizers, wave plates, and phase matching devices. The study on the optical anisotropy is of great significance for polarization-sensitive photodetectors and light emitting devices. In recent years, perovskites have received extensive attention due to their prominent optoelectronic properties and potential applications in optoelectronic devices. In particular, one dimensional perovskites are expect to exhibit large optical anisotropy due to the crystalline structure anisotropy. Together with the excellent optoelectronic properties of perovskites, we anticipate that one dimensional perovskites will find promising potential applications in the polarization-resolved optics. However, its optical anisotropy has been rarely reported. Our previous study has reported on the optical anisotropy of one-dimensional single chain perovskites, which exhibits a large emission linear dichroic ratio of 5.5 at room temperature. Nevertheless, this linear dichroic ratio is still not large enough for certain polarization resolved applications and far smaller than the linear dichroic ratio of the commercial optical elements. In this end, it is necessary to explore new materials to enhance the optical anisotropy.According to previous reports, it is possible to further increase the optical anisotropy by reducing the symmetry of the crystalline structure of a materials. By reducing the symmetry of the crystal structure, the octahedral structure of perovskites is more prone to distort, which increases the anisotropy of the transition dipole moment, thus increasing the optical anisotropy. Based on this principle, we design a one dimensional double chain perovskites, which will have a much lower symmetry compared with one dimensional one chain perovskites and thus can possibly exhibit a much larger optical anisotropy. The single crystal of one dimensional double chain perovskite C₅H₁₆N₂Pb₂I₆ crystals are synthesized via aqueous synthesis route. The as-synthesized crystals show needle-like shape with a length of 2~3 mm. X-ray diffraction pattern reveals the excellent crystal quality and one-dimensional nature of the crystals. Scanning microscope images show that the crystals have a rather smooth surface, which is beneficial for the spectroscopic measurement. The photoluminescence (PL) spectra of the as-synthesized crystals suggest that the spectral profile strongly depends on the excitation laser. Under a 405 nm laser excitation, the PL spectrum has a strong narrow emission peak at the high energy side and a weak broad emission peak at the low energy side while the spectrum is dominated by the broad emission peak when excited by a 473 nm laser. Nevertheless, both of those two emission peak show a linearly increase with the increasing the excitation power, which can exclude that those emission peaks are from defects or impurities. Together with previous studies, we assigne those two emission peaks as free exciton emission and self-trapped exciton emission. Since the broad emission can find important applications in white light emitting devices, we focus on the optical anisotropy of the broad emission peak hereafter.The temperature dependent polarization resolved PL studies have been carried out from 78 K to 260 K. For all temperature range we have investigated, a large optical anisotropy of PL spectra has been observed. At 78 K, the linear dichroic ratio can reach about 15.9, which is 7 times larger than that in a one dimensional single chain perovskite crystals (1.92). This observation confirms our hypothesis that reducing the symmetry of the crystalline structure of a material can indeed improve the optical anisotropy. The maximum linear dichroic ratio of our crystals appears at 110 K, which can be as large as 17.4, and also much larger than the maximum linear dichroic ratio in one dimensional single chain perovskite crystals (5.5). Finally, we have also extracted the complex dielectric constant, birefringence and dichroism of our crystals based on the reflection spectra via Kramers-Kronig relation. The birefringence and linear dichroic ratio reflect the real and imaginary part of complex dielectric constant, which are intrinsic properties of a materials and originated from the optical anisotropy of a material. The extracted dichroism and birefringence can reach 1.5 and 1.3, respectively. The birefringence of our crystals is much larger than the highest values reported in liquid crystals.In summary, the optical anisotropy of one-dimensional double chain perovskite crystals has been systematically studied, and the optical anisotropy of the crystals is proven to be improved by reducing the symmetry of crystals. Our study is of great significance for polarization sensitive optoelectronic devices based on one-dimensional double chain perovskites and shed light on how to further improve the optical anisotropy via deigning the crystal structure of a material.