In response to issues such as blurriness, low brightness, and poor contrast in underwater bridge pier crack images, this paper proposes an image enhancement method based on image fusion. Firstly, Homomorphic Filtering is applied to denoise the crack images, eliminating the noise impact of the underwater environment. Subsequently, the Homomorphic Filtering processed crack images are transformed from the RGB(Red,Green,Blue) space to the LAB space. The L channel in the LAB space is subjected to adaptive gamma correction for brightness adjustment, and the processed crack images are then converted back to the RGB space, resulting in enhanced crack images (Image 1). The crack images processed by homomorphic filtering are also subjected to contrast enhancement through contrast limited adaptive histgram equalization, producing contrast-enhanced crack images (Image 2). Finally, Image 1 and Image 2 are weighted fused to obtain the ultimate enhanced image. Subjective visual effects and three objective evaluation metrics are employed to validate the reliability of the proposed analysis method. The results indicate that the proposed method effectively enhances the brightness, clarity, and contrast of the crack images processed in this paper.