The invention discloses an active noise reduction method. The method comprises that present an error noise signal is collected regularly in a noise processing process; the weight is calculated according to the error noise signal, and a new weight coefficient is obtained; a reference signal in the present period is obtained according to the new weight coefficient and a harmonic component, which is generated in advance, of a preset fundamental frequency; according to the reference signal, a secondary signal whose frequency and amplitude are the same with those of the reference signal but phase is different from that of the reference signal is generated; and electric/acoustic conversion is carried out on the secondary signal to emit a secondary sound wave signal. According to the invention, it is not required to collect primary noise signals of a noise source, the reference signal is generated according to the harmonic component, which is generated in advance, of the preset fundamental frequency, and the stability is high. The invention also discloses an active noise reduction device which uses the method.