An embodiment of the present disclosure discloses a method and apparatus for annotating a medical image. An embodiment of the method comprises: acquiring a to-be-annotated medical image; annotating classification information for the to-be-annotated medical image, wherein the classification information comprises a category of a diagnosis result and a grade of the diagnosis result corresponding to the medical image; processing the to-be-annotated medical image using a pre-trained lesion area detection model, framing a lesion area in the to-be-annotated medical image, and annotating a lesion type of the lesion area, to enable the to-be-annotated medical image to be annotated with the lesion area and the lesion type of the lesion area; and splitting the framed lesion area from the to-be-annotated medical image with the framed lesion area to form a split image of the to-be-annotated medical image, to enable the to-be-annotated medical image to be annotated with the split image.