A method and a system for recognizing plant diseases and a recording medium are provided. The method includes: providing a plant disease database, for storing plant disease and disease characteristic image corresponding to the plant disease; after obtaining plant image by an image capture device, obtaining segmented plant image by an image processing unit according to a first processing technique, and obtaining suspected region image according to a second processing technique; calculating an area of the suspected region image, and when the area is greater than a preset area, using the suspected region image as syndrome image, and comparing the syndrome image with the disease characteristic image; and when the syndrome image matches any specific disease characteristic image, obtaining a corresponding specific plant disease.