The invention relates to a noise reduction wavelength tube, in particular to a noise reduction wavelength tube with the variable length. The noise reduction wavelength tube is used for eliminating the noise generated by an air inlet system of a vehicle, one end of the noise reduction wavelength tube is sealed, the other end of the noise reduction wavelength tube is communicated with the air inlet system, and the noise reduction wavelength tube is in a structure extending and retracting in the length direction, so the noise reduction wavelength tube can carry out length regulation according to the wavelength of noise to be eliminated, and the length of the noise reduction wavelength tube is equal to one fourth of the wavelength of the noise to be eliminated. The noise reduction wavelength tube can carry out length regulation according to the wavelength of the noise to be eliminated, and the length of the noise reduction wavelength tube is equal to one fourth of the wavelength of the noise to be eliminated, so the noise reduction wavelength tube provided by the invention can be applicable to different engines or vehicle types, and the universality of the noise reduction wavelength tube is improved.