With the development of intelligent power grid, an ultra-low power wireless monitoring platform applied on the tower is designed to improve the level of management and operation of transmission lines. Towers operating status and fault conditions could be monitored online by it. As a result of the level of 10mW power dissipation of MSP430 microcontroller and the Wake on Radio (WOR) Wireless communication module, the platform installed on the towers has the features of low power consumption and small size. A number of transmission line parameters can be monitored by the platform, such as lightning stroke flashover, pollution flashover, ice coating flashover, lightning stroke current, temperature, wind speed, and etc. The real-time data is transferred to the remote service supervising center progressively using custom wireless communication protocol. Power system managers in the monitoring center could be access to all the towers status and flashover fault conditions, and grasp the information of electric lines and deal with line faults timely, which could promote the intelligent management of the power grid. A transmission line tower flashover on-line monitoring device which can detect tower flashover current and fault-time is developed with the application of the monitoring platform.