The invention provides an alarm system for detecting abnormal operation of a wind power generator. The wind power generator is provided with a sound collection module, and the alarm system comprises asound collection module, an acoustic signal processing module, a fault diagnosis module and an early warning module; the sound collection module, the sound signal processing module, the fault diagnosis module and the early warning module are in turn connected, the early warning module is used for detecting the working state of the wind power generator, and if the wind power generator is found tobe abnormal, the early warning module sends an early warning message to remind maintenance personnel to perform maintenance. The system provides a simple, efficient and low-cost non-contact in-situ fault diagnosis method for wind power generator abnormality detection, and gives guiding suggestions for normal operation and maintenance of the wind power generator.