Abstract With widespread applications of digital coding metasurfaces in wireless communication, electromagnetic sensing, microwave imaging, radar detection, and other areas, their reliability and stability is becoming highly demanded. However, large‐scale digital coding metasurfaces may include tens of thousands of tiny elements, making it difficult for rapid and precise fault localization in complex environments using the traditional contact‐based diagnosis methods. To address this challenge, here an over‐the‐air fast diagnosis strategy is proposed with phase difference manipulation. By analyzing the correlation of scattering matrices through a limited number of measurements, the proposed method achieves precise localization of faulty elements. A proof‐of‐concept prototype is developed to demonstrate rapid diagnosis of a 10 × 10 array in 10 milliseconds, with broadband compatibility spanning 8–12 GHz and angular stability maintained within 40° incident angles. The proposed non‐contact diagnosis platform significantly reduces operational complexity and avoids potential errors or damage risks associated with the traditional methods, providing technical support for the practical deployment of large‐scale metasurface systems in 6G wireless communications and radar imaging.