The invention discloses a method for measuring the vibration mode of a tower, and the method comprises a measurement scheme and a mode algorithm. The method comprises the steps: installing an optical fiber sensor on a main material of a high-voltage transmission line tower, carrying out the temporal-spatial resolution vibration data detection, taking a theoretical mode as a basis set, and decomposing each mode intensity value through a vector decomposition algorithm. The method can fill a technical gap in the conventional field measurement of the vibration mode of the tower, and provides key data for the operation and maintenance of the tower.