Abstract: To detect airport runway in SAR image automatically, a new algorithm is proposed based on region segmentation and distance transform. The statistic information is used to enhance the contrast between runways and background，and 2-D histogram method is used to segment the image. Then, distance transform and partial space Hough transform is utilized to detect the center line of runways. Experimental results show that the algorithm can extract runways in large complex SAR images with good real-time performance.