The present invention provides a method and a device for adjusting a carrier frequency of a multiple-input multiple-output microwave device. The method includes: obtaining, by an indoor unit IDU, a frequency of a radio frequency-reference crystal oscillator and a first frequency multiplication factor of each outdoor unit ODU; selecting, by the indoor unit IDU, one of the frequencies of the radio frequency-reference crystal oscillator as a reference frequency; adjusting, by the indoor unit IDU, a carrier frequency of the multiple-input multiple-output microwave device according to the first frequency multiplication factor and a radio frequency offset between the reference frequency and the frequency of the radio frequency-reference crystal oscillator of each ODU.