The invention discloses a method for drawing up the center line of an arch dam. Firstly, the initially-drawn-up center line of the arch dam is obtained through a traditional computing method, then theinitially-drawn-up left (right) bank chord length Lsli (Lsri) is obtained through arch rings of different elevations, the function relationship curve of the elevation values of various layers of archrings and the initially-drawn-up left (right) bank chord length Lsli (Lsri) is obtained in a fitting manner through the principle of least squares, and the optimal center line position of the arch dam is obtained by computing the arch dam center offset distance obtained when the left and right bank computing chord length deviation under the elevations of the arch rings tends to be the minimum. According to the method, it is guaranteed that the left banks and the right banks of the arch rings tend to be symmetric, and the repeated and complex manual trial process is avoided.