The present invention discloses a headset, a terminal, and a method for processing an audio signal based on the headset and the terminal. The method for processing an audio signal includes: acquiring, by a first microphone of a headset in a call process, a first audio signal including a call voice and background noise, and acquiring, by a second microphone of the headset in the call process, a second audio signal including the background noise; and transmitting, by using an external plug of the headset, the first audio signal and the second audio signal to a noise reduction chip built in a terminal, so that the noise reduction chip performs noise reduction processing on the first audio signal according to the second audio signal.