Abstract: 【OBJECTIVE】A novel method for measuring area of corn leaf is proposed using Image processing software developed with Visual C++6.0 based on image processing techniques and Digital Cameras. 【METHOD】Firstly, corn leaf and reference board which are hung in the vitical wall are captured by a color digital camera in the same image. Secondly, the blue component of the image are extracted, the noise are eliminated used the median filtering、dilation and erosion. the corn leaf are segregated from the background by Ostu threshold segrement method. Thirdly, every reginal of the object is labeled and calculated its’ pixel number. Lastly, the corn leaf’s real area can be got through the corn leaf’s pixel number and the image resolution ratio.【RESULT】The result shows that there are close relationships between digital image processing method and “Maximum length ×width”ruler method, and digital image is more accurate than the “Maximum length ×width”ruler method. 【CONCLUTION】This kind of shooting method can avoid engendering the geometric distortion. the intensity of the object and the background has the most different in the blue component of the image.