The invention relates to an offshore non-repetitive time-lapse seismic frequency-division equilibrium processing method characterized in comprising the following steps: 1, basic data and monitoring data in a same to-be-explored work area is obtained; 2, the basic data and the monitoring data are respectively subjected to frequency division processing to perform non-repetitive noise frequency-dependent characteristic analysis, and frequency division filtering is carried out on the basic data and the monitoring data according to the non-repetitive noise frequency-dependent characteristic analysis result; 3, the basic data and the monitoring data obtained through the frequency division filtering is subjected to overall amplitude correction to obtain the basic data and the monitoring data, of which the amplitude levels are consistent; 4, matched filtering correction is separately carried out on the basic data and the monitoring data which have been subjected to amplitude correction to obtain the basic data and the monitoring data, of which the amplitude levels are consistent; and 5, the basic data and the monitoring data which have consistent frequency spectrum characteristics are subjected to time-varying travel-time correction to obtain the basic data and the monitoring data, of which the time-varying travel-time are the same so as to complete cross-equilibrium processing of the basic data and the monitoring data.