Direct X-ray detectors, which can convert an X-ray signal into electrical current with superior sensitivity, are of great interest for a wide range of applications, including medical diagnostics, security screening, and nondestructive product testing. Halide perovskites are a recently demonstrated new X-ray detection candidate due to their excellent optoelectronic characteristics and robust fabrication. However, toxicity issues from both the materials and processing process, and lack of high quality large-area halide perovskite films for stable X-ray detectors are obvious obstacles to their practical application. Here, we explored green methylammonium acetate (MAAc) solvent blade-coated lead-free methylammonium bismuth iodide (MA₃Bi₂I₉) films for direct-conversion X-ray detectors. Methylamine chloride (MACl) was used as an additive to improve the quality of the MA₃Bi₂I₉ films, resulting in X-ray detectors with a sensitivity of 100.16 μC Gy_air⁻¹ cm⁻², and a low limit of detection of 98.4 nGy_air s⁻¹. This research provides a green method for preparing perovskite X-ray detectors.