The line tree distance refers to the shortest distance between the transmission line and the tree, and this distance directly reflects the risk probability of a tree barrier accident on the power transmission line. This paper relies on the principle of photogrammetry to match and obtain point cloud information along the power transmission line from the stereo pairs of satellite remote sensing images, thereby constructing a three-dimensional model along the transmission line. On this basis, the supervised classification method is used to identify and extract the spatial parameters of the canopy area, and the catenary equation of the power transmission line is used to obtain the spatial parameters of the transmission line, thereby realizing the measurement of the distance between the line and the tree. According to the actual measurement of ±800 kV Fufeng and Jinsu line, the maximum measurement error of the proposed method for tree crown elevation is 10.69%, and the maximum measurement error for line tree distance is 15.80%. This method pinpoints 20 key concerned intervals, and can realize regular, wide-range, high-precision, risk-free and economical measurement of line-tree distance and timely warning of tree obstruction risk.