The invention discloses a lead ice monitoring method and system based on three-dimensional reconstruction. The lead ice monitoring method comprises the steps: 1, installing two cameras which are different in position and have a certain angle for imaging a lead to be monitored, obtaining a boundary contour of the lead to be monitored; 2, acquiring ice images of the lead to be monitored, shot under the ice condition; 3, processing the ice images of the two cameras, which are obtained from the same section of line from different angles, to ensure that image points of the same point on an ice line in two images show different vision positions, obtaining a geometrical relationship between the two image points according to a camera imaging principle, and further figuring out three-dimensional coordinates of this point; 4, reconstructing a three-dimensional mode of line icing through acquiring the data of the three-dimensional coordinates of a large quantity of characteristic points; and 5, comparing the three-dimensional mode of the line icing with the boundary contour of the lead to be monitored, and figuring out an ice thickness. The invention provides a lead ice monitoring method and system based on three-dimensional reconstruction, which are capable of carrying out remote real-time monitoring on ice.