The invention discloses a retinal vessel segmentation method and system based on a retinal fundus image, and belongs to the technical field of image processing, and the method comprises the steps: obtaining a to-be-detected retinal fundus image; constructing a basic module according to the retinal fundus image features; cascading N basic modules to serve as a final network model, the to-be-detected retinal fundus image serving as input of the whole network model, and obtaining a segmentation result of retinal vessels. The foreground characteristics of the previous basic module and the originalpicture are transmitted to the next basic module together, so that the rear basic module can inherit the learning experience of the front basic module, the training process is accelerated, and the problem of data imbalance is effectively solved; the to-be-detected retinal fundus image is used as the input of the overall model S-UNet, and the obtained segmentation result of the retinal blood vessel is more accurate.