The invention discloses a power transmission line swing track multi-dimension monitoring system and monitoring method. The monitoring system comprises multiple wireless inertia measuring units, a tower data pre-processing unit, and a monitoring unit. The multiple wireless inertia measuring units are arranged on leads respectively. The tower data pre-processing unit is arranged on a tower. The monitoring unit is arranged in a monitor station. The wireless inertia measuring units are connected to the tower data pre-processing unit through wireless signals. The tower data pre-processing unit is connected to the monitoring unit through the Ethernet. The three-dimensional motion tracks of the leads are measured by the inertia measuring units, and are sent to and pre-processed by the tower data pre-processing unit through wireless transmission. Then, data is sent to the monitoring unit through the Ethernet, and the monitoring unit calculates and displays the swing tracks and the swing characteristic values of the leads. The monitoring system can accurately monitor the three-dimensional swing track of a power transmission line in real time, allows people to timely find a power transmission line that may undergo accident hidden troubles, and thus economic losses are avoided.