The invention relates to a noise reduction device of a range hood. The noise reduction device is characterized in that a fan inlet is detachably provided with a lower noise-damping device; the lower noise-damping device comprises at least one noise-damping unit; the noise-damping unit comprises a longitudinally arranged noise-damping pipeline; the upper end of the noise-damping pipeline is communicated with the fan inlet, and the lower end of the noise-damping pipeline is communicated with the air outlet of a fume collecting hood; the air inlet end of the noise-damping pipeline is provided with a speaker, the inner wall of the noise-damping pipeline is provided with a reference microphone and an error microphone which is positioned below the reference microphone; and the reference microphone, the error microphone and the speaker are controlled by an active noise reduction controller. The noise reduction device disclosed by the invention can realize the noise reduction without improving the internal structure of the range hood but just by detachably arranging the lower noise-damping device on the fan inlet, the noise-damping device can be assembled and dissembled freely, so that good universality and adaptability are achieved, the problem of noise at the air inlet of the rang hood can be well solved, and the problem of noise of the air outlet of the range hood can be solved by detachably arranging an upper noise-damping device on a fan outlet.