The Hough Transform (HT), the Radon Transform (RT) and the Line Segment Detector (LSD) are the most well-known methods for line detection. But the HT and RT methods cost large computing consumption and always resulting a poor performance with many outliers. The LSD method is not effective to the real application of complex background condition. In this paper, a boundary search radon transform (BSRT) approach is proposed for high voltage transmission line detection in Unmanned Aerial Vehicle (UAV) based routing inspection. The core idea assumes that the initial point of an integral line is on one of the four image boundaries, so it isn't always necessary to analyze all points in an image and a new line detection strategy is designed. Comparing to the HT, RT and LSD methods, our method is validated by the experimental results to be fast, efficient and reliable to complex environments.