The growth status of roots can reflect the region's climate and soil characteristics, and whether the root is flourishing or not can response the whole plant's health. Research on the ecological parameter of root is the foundation of the root's growth condition. Manual processing of minirhizotron images is time-consuming and strenuously, this paper puts forward a kind of automatic segmentation method in minirhizotron images. It extracts centerlines of minirhizotron images based on ridge detection, then comp...