A new grayscale image authentication method with a pixel-level self-recovering capability for tampered region repairing is proposed. By dividing the grayscale range into bins, a 3-bit bin code is generated as the authentication signal for each pixel in the input cover image. The authentication signals then are embedded randomly into the image pixels for the double purposes of tampering localization and data repairing in the image authentication process. This leads to great saving of storage space for embedding the signals and recovery data, and so results in the possibility of pixel-level authentication. Tampered pixel repairing is conducted by retrieving the embedded bin code to obtain a corresponding representative value for use as the new gray value of the tempered pixel. Good experimental results show the effectiveness of the proposed method.