An event detection method is for detecting if an event being predetermined exists in a detected environment, in which a first wireless unit, at least one second wireless unit wirelessly communicating with the first wireless unit, and at least one cooperating detection device are disposed. The event detection method includes a live CSI data obtaining step, a live CSI data reducing step, a cooperating data obtaining step and an event determining step. The live CSI data reducing step includes reducing a size of a plurality of live CSI data to generate a plurality of preprocessed live CSI data. The event determining step includes inputting the preprocessed live CSI data to an event classifier and processing a plurality of cooperating data to determine if the event exists.