A method for Voice Activity Detection, VAD, comprising: acquiring a fluctuant feature value of a background noise when an input signal is the background noise, wherein the fluctuant feature value is used to represent fluctuation of the background noise; performing adaptive adjustment on a VAD decision criterion related parameter according to the fluctuant feature value, wherein the VAD decision criterion related parameter comprises a hangover length; and performing VAD decision on the input signal by using the VAD decision criterion related parameter on which the adaptive adjustment is performed, wherein the fluctuant feature value is specifically a background noise frame signal-to-noise ratio, SNR, long term moving average snr n _mov, and the acquiring the fluctuant feature value of the background noise when the input signal is the background noise comprises: receiving a current frame of the input signal; deciding whether the current frame is a background noise frame according to a VAD decision criterion; and acquiring a background noise frame SNR long term moving average snr n _mov by using the formula snr n _mov = k·snr n _mov + (1- k) ·snr, when the current frame is the background noise frame, wherein snr is an SNR of a current background noise frame, and k is a forgetting factor for controlling an update rate of the background noise frame SNR long term moving average snr n _mov. acquiring a fluctuant feature value of a background noise when an input signal is the background noise, wherein the fluctuant feature value is used to represent fluctuation of the background noise; performing adaptive adjustment on a VAD decision criterion related parameter according to the fluctuant feature value, wherein the VAD decision criterion related parameter comprises a hangover length; and performing VAD decision on the input signal by using the VAD decision criterion related parameter on which the adaptive adjustment is performed, wherein the fluctuant feature value is specifically a background noise frame signal-to-noise ratio, SNR, long term moving average snr n _mov, and the acquiring the fluctuant feature value of the background noise when the input signal is the background noise comprises: receiving a current frame of the input signal; deciding whether the current frame is a background noise frame according to a VAD decision criterion; and acquiring a background noise frame SNR long term moving average snr n _mov by using the formula snr n _mov = k·snr n _mov + (1- k) ·snr, when the current frame is the background noise frame, wherein snr is an SNR of a current background noise frame, and k is a forgetting factor for controlling an update rate of the background noise frame SNR long term moving average snr n _mov. receiving a current frame of the input signal; deciding whether the current frame is a background noise frame according to a VAD decision criterion; and acquiring a background noise frame SNR long term moving average snr n _mov by using the formula snr n _mov = k·snr n _mov + (1- k) ·snr, when the current frame is the background noise frame, wherein snr is an SNR of a current background noise frame, and k is a forgetting factor for controlling an update rate of the background noise frame SNR long term moving average snr n _mov.