The invention relates to a noise processing technology in a prefabricated cabin, and specially relates to a noise reduction method for a prefabricated cabin type transformer substation. The noise reduction method for a prefabricated cabin type transformer substation is also suitable for noise processing for a transformer in an enclosed space, and includes the steps: providing a noise reduction system, respectively acquiring the measurement noise s(n) of a noise source, the noise b(n) transmitted to the cabinet body from the transformer and the environment sound e(n) so as to obtain the sound wave amplitude and waveform of the noise; calculating the times of the noise in the cabin and the noise source noise to obtain the gain value; according to the reverse sound wave principle, and obtaining the corresponding reverse sound wave on the basis of the gain value; and outputting the sound wave being able to counteract of the noise in the cabin through a reverse sound wave output device. The noise reduction method for a prefabricated cabin type transformer substation uses the gain to perform timed verification so as to effectively reduce the noise in the limited space, thus improving the operating environment of operation staff, improving work efficiency and improving work safety.