Abstract: Mark point is widely used in image-based outdoor measurement. However,the existing method of mark point recognition and location is inaccuracy. Aimed at the inaccuracy of mark point recognition and location in image-based outdoor measurement,we proposed a method of mark point design and recognition. This method first designed the color and size of mark point,and then presented the recognition and location method based on HSI color space,which include the image binarization by HIS color space,the screening by shape criteria,and the center location by secondary ellipse fitting. Finally the method was tested experimentally. The experiment results show that the method is more accuracy,and suitable for image-based outdoor vision measurement.