The present invention belongs to the field of network communication technology. The dynamic distribution method for slot bandwidth in exchanger includes setting slot number N for dynamic bandwidth distribution and bandwidth to be distributed B, determining the minimum distributed bandwidth unit deltaB, connecting all the upstream bandwidth in the N slots to the exchange board, setting one-out-of-N selectors in the number of B/deltaB and with the input of NXdeltaB, performing logic control of one-out-of-N selectors, and distributing the bandwidth to gated slots. The method is flexible and high in distribution and makes it possible to utilize valuable upstream bandwidth resource fully.