Lead halide hybrid perovskite ferroelectrics show great potential in the field of self-powered X-ray detection due to their excellent X-ray absorption, high carrier mobility, large carrier lifetime, and interesting ferroelectricity. Nonetheless, the toxicity of lead raises concerns regarding safety for humans and the environment, which limits their practical applicability. Herein, we successfully realized stable self-powered X-ray detection with a low detection limit using a lead-free halide hybrid perovskite ferroelectric crystal, [H₂mdap]BiBr₅ (1, H₂mdap = N-methyl-1,3-diaminopropanium), driven by the switchable spontaneous polarization (P_s). Specifically, a remarkable switchable ferroelectric-photovoltaic (FE-PV) effect and excellent open-circuit photovoltage under X-ray irradiation endow 1 with a self-powered detection capability. Strikingly, the 1 detector shows a relatively high sensitivity of 79.0 μC Gy⁻¹ cm⁻² under 22 keV X-rays and achieves a low detection limit of 28 nGy s⁻¹ at zero bias, much lower than that of the regular medical diagnosis (∼5.5 μGy s⁻¹). Additionally, 1 also shows good operational stability, which may benefit from a stable structure and high activation energy (E_a). This study successfully demonstrates self-powered X-ray detection in 1D lead-free ferroelectric materials, which opens up new possibilities for safe and stable X-ray detection.