X-ray detection is of great significance for medical diagnostics, security inspection, and homeland security. The fabrication of a high-sensitivity X-ray detector can reduce the X-ray dose, especially in medical and security inspections. In this paper, the high-quality CsPbBr3 single-crystal film was prepared by a space-confined method. Then an X-ray detector with good performance based on the film were fabricated. The morphology, thickness, composition, and orientation of the films were analyzed by the polarizing microscope, scanning electron microscope equipped with EDS, and EBSD detector. It is found that the prepared single-crystal films have a flat, smooth surface, uniform element distribution, and homogeneous crystal orientation. The detector has high resistivity of 7.23×108 W·cm and an extremely high sensitivity of 2 610 μC·Gy-1·cm-2.