Abstract: In order to meet the demand of the identification, a X-ray digital image adaptive enhancement algorithm based on neighborhood contrast was proposed. Firstly, the imaging characteristic of the Image Quality Indicator(IQI) was analyzed based on minimum defect method. Subsequently, the neighborhood selection principle was determined according to the corresponding requirement for the highest resolution. After comparing the contrast relationship within the neighborhood, the adaptive mapping function was derived. Finally, the image contrast was enhanced. Both of the global and local quality of the images can be enhanced efficiently based on the algorithm. The distortion is also well suppressed. It is suitable for not only enhancement of X-ray digital images, but also regular grayscale images.