A sound password unlocking method, comprises unlocking procedures: collecting a sound password signal that the user plays and performing the analog to digital conversion (11); Inputting the converted sound password signal to a reference signal input end of an adaptive noise cancellation module; inputting an original signal to an original signal input end of the adaptive noise cancellation module; producing a first output signal in adaptive noise cancellation (12); Calculating the difference between the first output signal and the original signal (13); Comparing the difference between the first output signal and the original signal with a standard difference; determining the sound password is correct if the two difference values are identical and enabling the motor to drive a lock cylinder to open otherwise no unlock operation executed (14). The sound password unlocking method provided by the present invention, based on adaptive noise cancellation is hard to be cracked, which is reliable and safe. The lock could be locked by sound password recognition.