Abstract: Wind turbine blades are one of the key equipment of wind turbines. Quick, accurate, and effective fault diagnosis of blades is of great benefit to improving the safety and economy of the unit. Therefore, scientific and technological personnel have explored various methods to diagnose blade faults. Currently, these methods have their own advantages and disadvantages, and there is still a distance from large-scale practical application. This article first introduces and summarizes the common fault types of fan blades, and then introduces the existing fault diagnosis technologies for fan blades from six aspects: computer vision, vibration signal analysis, infrared thermal imaging, ultrasound, and sensors. The characteristics of these technologies are analyzed, and the advantages and limitations of existing detection technologies are systematically elaborated, Finally, the main directions for the future development of fan blade fault diagnosis technology were discussed from the perspective of improving the safety and economy of the unit.