The invention provides a measuring method for foundation displacement of a power transmission tower. The measuring method comprises the following steps of measuring point and reference point setting, initial coordinate obtaining, detector installing and foundation displacement measuring. According to the step of measuring point and reference point setting, measuring points are set up at all tower feet of the power transmission tower correspondingly, and a reference point is set in the position with the preset distance from the center position of the power transmission tower. According to the step of initial coordinate obtaining, initial three-dimensional coordinates of all the measuring points are obtained. According to the step of detector installing, detectors used for coordinate detection are installed at the reference point and all the measuring points correspondingly. According to the step of foundation displacement measuring, the foundation displacement value of the power transmission tower is determined according to the three-dimensional coordinates, detected by the detectors, of all the measuring points, and the initial three-dimensional coordinates of all the measuring points. According to the measuring method provided by the invention, the foundation displacement of the power transmission tower is monitored synchronously in real time through the detectors, three-dimensional space coordinates of the power transmission tower foundation are obtained precisely, a basis is provided for security state evaluation of a power transmission tower structure in a gob affecting zone, and better applicability and higher precision are achieved.