Disclosed is a blind authentication method for a frequency selective fading channel based on a smoothing technique. The method includes: transmitting carrier signals to a frequency selective fading channel having multiple paths, where each carrier signal includes an authentication signal, a pilot signal and an information signal, receiving the carrier signals, performing BKIC processing on a carrier signal in each path to obtain a target signal, and performing differential signal processing on the target signal to obtain a target authentication signal, obtaining a reference signal based on a key and the pilot signal in the each path, performing the differential signal processing on the reference signal to obtain a reference authentication signal, and calculating a correlation between the target authentication signal and the reference authentication signal to obtain a test statistic; and comparing the test statistic with a prescribed threshold to determine whether the carrier signal in the each of the plurality of paths can pass authentication.