The invention provides a multicarrier filtration method, a multicarrier filtration system and a repeater, which are suitable for the field of communications. The multicarrier filtration method comprises the following steps of: using a plurality of continuous carrier waves as a subband by a control module to obtain carrier frequency, carrier quantity and subband quantity; determining the center frequency of the subband according to the carrier frequency and the carrier quantity; distributing corresponding subband passband width and subband stop-band width to the subband according to the passband width and the stop-band width of the carrier waves in the subband and the carrier quantity; determining channel bandwidth of the subband; moving the center frequency of the subband to zero frequency by a lower frequency conversion module; carrying out corresponding multiple filtration extraction on the subband by a filtration extraction module; and carrying out channel filtration by a channel filtration module according to the corresponding subband passband width and the corresponding subband stop-band width distributed by the control module and the determined channel bandwidth of the subband. The multicarrier filtration method, the multicarrier filtration system and the repeater can save resources, reduce filtration step number, shorten time delay and satisfy higher index requirements.