In this paper, we present a detection algorithm of high-voltage line based on Hessian matrix for the application background of high-voltage line inspection of Unmanned Aerial Vehicle(UAV). Firstly, we extract the direction of linear object according to the eigenvector direction of Hessian matrix. Secondly, we extract the point of approximate eigenvector direction to compose the line segment using the region growing method. Finally extracting the linear object from these line segment using the statistical method to make the line segment most and longest along the linear object. The results of experiment show that our method can detect high-voltage line accurately and satisfy the requirement of UAV line inspection for precision and speed.