Abstract: In order to improve the efficiency of intelligent operation and maintenance of wind farms and avoid the risk of blades deformation,cracking or even explosion damage after the disconnection of wind turbines blades lower lead,this paper proposes a wind turbines blades lower lead disconnection online monitoring system based on single wire transmission technology,embedded technology,GPS positioning and 4G communication technology. It realizes the real-time collection of the information of the under-blade lead state without stopping and climbing the tower for inspection. Simulations and experiments show that the system can effectively,stably and accurately identify the disconnection fault of the under-blade leads.