The invention relates to the plant leaf area measuring technology field, to be specific, relates to a leaf area measuring method based on digital camera images. The leaf area measuring method comprises steps that (1) a black comparison scale is produced; (2) a to-be-measured leaf and the comparison scale are laid on a white background, and the comparison scale cannot be shielded by the leaf, and the digital camera is used to acquire the color images of the leaf and the color images of the comparison scale; (3) according to G and B of every pixel of the acquired color images, the area of the leaf and the area of the scale are determined and identified; (4) the number of the pixels of the leaf and the number of the pixels of the scale are counted respectively, and the area of the leaf is calculated. The leaf area measuring method has advantages of time saving, labor saving, low costs, and high accuracy.