0.5μm。For non-contact and high accurate measurement of grape stem diameter, a method based on computer vision was proposed. Bilateral filtering was implemented for smoothing original grayscale images. Furthermore, the grape stem was extracted from the background by Otsu and BloB analysis. According to the localized feature point, the position of stem diameter was determined. Then the stem diameter was calculated by the pixel size coefficient and the pixels of the stem diameter. Consequently, continuous stem diameter measurement was achieved. Field applications and experimental results show that the repeatability accuracy of the system achieves ±0.5 μm. 