In order to study the dynamic response of power transmission lines under mechanical fault, the structural dynamic response monitoring indexes based on the requirement of field measurement were determined according to the structural characteristics of steel towers. The monitoring program was put forward in terms of the monitoring principle and basis of the sensors. The vibration characteristic, dynamic alignment and stress/strain are chosen to be the monitoring indexes. Considering the synchronization function of GPS system, the three monitoring indexes of the large span high voltage tower can be simultaneously monitored by using vibration sensor, GPS and strain sensor. The monitoring scheme can provide the theoretical base for the establishment of early warning system and the collection of dynamic response of steel tower during line break or tower collapse.