The invention provides a retinal blood vessel morphology quantization method based on a connected region. The method obtains a retinal blood vessel segmentation image after the fundus image is preprocessed, and then performs post-processing on the blood vessel segmentation image. On this basis, the vascular network is thinned and boundary treated, and the vascular centerline network and vascular boundary map are obtained. Corner detection is then performed and removed from the vascular centerline network so that the vascular segments of the vascular network form separate communication areas. Traversing is performed on the blood vessel segment, approximate the centerline of the blood vessel segments, and the blood vessel segment is changed into a broken line to calculate the direction of the blood vessel. At last, that initial diameter value is calculated, the center of the circle is selected by sliding on the centerline of the blood vessel segment, a semicircle window is created according to the direction of the circle cardiovascular and the diameter value measured in the early stage, and the distance between the window and the two intersection points of the blood vessel boundary is taken as a new diameter value. From this iteration, a set of vessel diameter values are measured, and the median value is the vessel diameter of the vessel segment. The invention is applicable to the quantification of large-scale retinal blood vessel morphology, and has high reliability.