The invention discloses a method and system for determining displacement and settlement of a transmission line based on Beidou positioning, and relates to the field of transmission line maintenance. The method comprises the following steps of calculating the coordinates of a transmission tower based on Beidou positioning and using a differential positioning algorithm at the current moment; calculating the current and previous shape variables of the fixed-point specified direction coordinates set by the transmission tower, and removing the gross errors in the previous shape variables; sorting the previous shape variables according to the chronological order to establish a prediction model; predicting the deformation variables at the fixed point in the specified direction at the current timebased on the established prediction model, and taking the deformation variables as the displacement settlement determination thresholds; and comparing the calculated current deformation variables atthe fixed point in the specified direction with the displacement settlement determination threshold to obtain a judgment result of the displacement and settlement of the transmission line. The invention can realize the accurate judgment of the displacement and settlement of the transmission tower.