The invention discloses a high-voltage transmission line fatigue monitoring system, and relates to the technical field of mechanical vibration or ultrasonic detection devices. The monitoring system comprises a plurality of line fatigue early-warning devices installed on a transmission line, a line monitoring base station, a WEB server, a data backup server, a plurality of Internet user terminals, a user base station and a plurality of mobile user terminals. The system can monitor vibration and ultrasonic echo conditions of the transmission line in real time through the line fatigue early-warning devices, analyze the fatigue conditions of the line, send out warning information, assist operation departments in effectively maintaining the transmission line, and avoid the line breakage accident which is caused by breeze vibration to the transmission line.