The invention relates to a failure detection system for a wind power blade. The failure detection system for the wind power blade comprises an unmanned aerial vehicle, and a video capturing device and a first signal emitting-receiving device both arranged on the unmanned aerial vehicle, wherein the unmanned aerial vehicle performs data interaction with a central server through the first signal emitting-receiving device, and the central server is provided with a second signal emitting-receiving device, a data acquisition device and an image failure signal identification device connected sequentially; the failure detection system for the wind power blade further comprises a wind power generation set, and a third signal emitting-receiving device and a second anemograph interconnected and both arranged on the wind power generation set, wherein the wind power generation set performs data interaction with the central server through the third signal emitting-receiving device. The failure detection system for the wind power blade has the excellent effects that the unmanned aerial vehicle is provided with the video capturing device to monitor and grasp blade states of the wind power blade under various conditions in real time, thus, the wind power blade can be detected and maintained in a targeted manner, workload of maintenance personnel is reduced, meanwhile, a wind power field is guaranteed to operate steadily under the condition of plenty of wind, and economic benefit is improved.