The quality of the fingerprint images greatly affects the performance of the minutiae extraction. In order to improve the performance of the system, many researchers have been made efforts on the image enhancement algorithms. If the adaptive preprocessing according to the fingerprint image characteristics is applied in the image enhancement step, the system performance would be more robust. In this paper, we propose an adaptive preprocessing method, which extracts five features from the fingerprint images, analyzes image quality with Ward’s clustering algorithm, and enhances the images according to their characteristics. Experimental results indicate that the proposed method improves both the quality index and block directional difference significantly in a reasonable time.