Blades are the key load-bearing components that convert wind energy into electric energy. The complex forces

high failure rate and high maintenance cost have always been prominent problems restricting the safety and economy of wind turbines. To improve the development of in-service safety guarantee technology for wind turbine blades

the commonly used monitoring methods for blades are reviewed according to the monitoring principle. The commonly used blades monitoring methods can be divided into two types: the contact monitoring methods based on vibration signal and mechanical waves

and the non-contact monitoring methods based on thermodynamics and optics. The contact monitoring methods determine the safety state of the blade through the time-frequency

frequency spectrum and other information of the blade vibration signal or the strain energy released when the blade is damaged. The non-contact monitoring methods can be divided into infrared thermal imaging

laser Doppler velocimetry and computer vision monitoring methods. The research progeress and application status of various blade monitoring mthods are presented. Finally

suggestions and prospects are put forward for the application of blade condition monitoring methods in actual wind turbines.