Cs3Bi2I9 single crystals were prepared by evaporative crystallization method at the conditions of low temperature and atmospheric pressure, with temperature ranging from 60 ℃ to 90 ℃ and holding time ranging from 18 h to 30 h. The effects of temperature and holding time on the crystal structure and optical properties of Cs3Bi2I9 single crystals were investigated. The Cs3Bi2I9 single crystal film based on flexible substrate was prepared by mechanical exfoliation method and its electrical properties were studied. The results show that, for the best crystallinity target, the optimal parameters for the growth of Cs3Bi2I9 single crystals are the temperature of 60 ℃ and holding time of 26 h. The effects of temperature and holding time on the crystallinity, ultraviolet visible light absorbance, and photoluminescence properties of Cs3Bi2I9 single crystals are consistent. The flexible Cs3Bi2I9 single crystal film has obvious photoelectric properties, and shows excellent stability during work. Cs3Bi2I9 single crystal film has outstanding bending durability. After bending 100 times at the angle of 90°, the performances of Cs3Bi2I9 single crystal film still maintain at 84.4% of the original performances. Lead-free perovskite Cs3Bi2I9 single crystal film has potential application prospects in flexible photoelectric sensor devices.