Sensitive, flexible, and low false alarm rate X‐ray detector is crucial for medical diagnosis, industrial inspection, and scientific research. However, most semiconductors for X‐ray detectors are susceptible to interference from ambient light, and their high thickness hinders their application in wearable electronics. Herein, a flexible visible‐blind and ultraviolet‐blind X‐ray detector based on Indium‐doped Gallium oxide (Ga2O3:In) single microwire is prepared. Joint experiment−theory characterizations reveal that the Ga2O3:In microwire possess a high crystal quality, large band gap, and satisfactory stability, and reliability. On this basis, an extraordinary sensitivity of 5.9 × 105 µC Gyair−1 cm−2 and a low detection limit of 67.4 nGyair s−1 are achieved based on the prepared Ag/Ga2O3:In/Ag device, which has outstanding operation stability and excellent high temperature stability. Taking advantage of the flexible properties of the single microwire, a portable X‐ray detection system is demonstrated that shows the potential to adapt to flexible and lightweight formats. The proposed X‐ray detection system enables real‐time monitor for X‐rays, which can be displayed on the user interface. More importantly, it has excellent resistance to natural light interference, showing a low false alarm rate. This work provides a feasible method for exploring high‐performance flexible integrated micro/nano X‐ray detection devices.