Abstract: The present invention discloses a noise-reduction method and device for self-adaptively adjusting a noise reduction gain, and a noise reduction earphone. The method includes: receiving a voice signal collected by a microphone installed on an earphone receiver as a noise signal; obtaining a current noise level of an external environment according to a current sound intensity of the noise signal; setting a current noise reduction gain value corresponding to a current noise level; and performing a noise reduction processing on the noise signal according to a current noise reduction gain value. The present invention sets a noise reduction gain value corresponding to a current noise level of an external environment according to the current noise level, which enables the noise-reduction earphone to adaptively adjust a noise reduction gain and effectively improves the user experience.