In the background of the application of UAV to the power line inspection, a new power line detection method based on UAV image is proposed in order to convenient analyzing the power line. First, an adaptive threshold Canny edge detection method based on Otsu is proposed, which is used to detect the edge of the power line. Then, the binary images obtained by the edge detection are processed by mathematical morphology, and the line segment detection is carried out by Hough transform improved by fractional look-up table method. Finally, a method based on line to line spatial information analysis is proposed to screen and fit the line segments. The experimental results on UAV images show that the proposed power line detection method is a well performance power lines detection method, which is based on UAV images.