Because of its stable chemical properties and wide band gap, CsPbCl 3 perovskite has shown great application prospects in ultraviolet photodetectors (UPDs). However, the poor solubility of CsCl in organic solvents impedes the fabrication of high-quality CsPbCl 3 films. Herein, we introduced an A-site substitute route for fabricating a high-quality CsPbCl 3 microcrystalline (MC) film by spin-coating cesium acetate on a MAPbCl 3 MC film followed by a high-temperature annealing process. To enhance the device performance of the FTO/SnO 2 /CsPbCl 3 MCs/carbon structure UPD, a pressure-assisted annealing strategy was carried out, which reduced the void density and surface roughness of the microcrystal film. Finally, our optimized PDs showed high device performances with an on/off ratio of 6 × 10 4 , a responsivity of 0.13 A W -1 , a detectivity of as high as 1.07 × 10 12 Jones, and a rise/fall time of 10/24 μs. Moreover, our unpacked PDs showed good storage and light stability. Our results lay a foundation for the application of all inorganic perovskite in the ultraviolet region.