A rapid detection method of crop-row based on improved Hough transformation was suggested to detect the position of crop-rows after analyzing the characteristics of field crop planting. The true color images containing crop-row and soil background were captured as the research objects. Since the histogram projection is easily disturbed by external factors and the Hough transformation has a low speed, a combination of these two algorithms was developed. First, a true color image of field crops was processed with 2G—R—B gray and OTSU to separate plants from soil. Second, the noise was eliminated by fast median filtering algorithm, and then the image was divided into ten horizontal strips to get the anchor points according to the geometric distribution of the crop-rows. Finally, the centerline of crop rows was obtained by Hough transformation using those points. Test results show that the processing speed of the improved Hough transformation method is four times faster than that of original Hough transformation with the similar positioning accuracy, and the centerline detected can highly match the crop-row. 