The invention relates to a power transmission line monitoring system, in particular to a power transmission line intelligent monitoring system based on the network of things. A monitoring management main machine collects data collected by a monitoring front end and stores the data through a multi-layer data concentrator, and the monitoring management main machine is connected with a superior centralized control management main machine through a power communication network. Subsystem tower extensions and monitoring devices that the extensions correspond to are arranged at the monitoring front end. The monitoring management main machine distributes identification (ID) domains for lower-layer data concentrators, distributes ID sub domains for the subsystem system tower monitoring extensions of a data collection layer and distributes fixed ID for each monitoring device, and the subsystem tower monitoring extensions are communicated with the data concentrators in the wireless communication mode. The system utilizes the technical characteristics of the network of things, and is formed by combining various intelligent monitoring systems of a power transmission line.