Because of its stable chemical properties and wide band gap, CsPbCl3 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 CsPbCl3 films. Herein, we introduced an A-site substitute route for fabricating a high-quality CsPbCl3 microcrystalline (MC) film by spin-coating cesium acetate on a MAPbCl3 MC film followed by a high-temperature annealing process. To enhance the device performance of the FTO/SnO2/CsPbCl3 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 × 104, a responsivity of 0.13 A W-1, a detectivity of as high as 1.07 × 1012 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.