Abstract: To measure plant leaf area quickly and accurately, a method of plant leaf area measurement based on color channel similarity image segmentation was put forward. In this paper, plant leaf area was separated by using the color channel similarity and an auto adaptive threshold. After the pixels of the leaf area and the referenced rectangle were counted, the leaf area was calculated. Experiments showed that this method was more accurate and had a strong robustness to the shadow and piebald, and the misclassification error was only 1.23%. So this method greatly improves the accuracy of measurement and is a practical method of plant leaf area measurement by taking pictures and can be embedded in mobile devices such as smart mobile phones.