EPON (Ethernet Passive Optical Network) is a rising bandwidth access technology, and it could realize the comprehensive operation access including data, video, and voice, with good economic characters. IEEE 802.3 ah is the industrial standard of EPON, but it doesn’t concretely regulate the uplink bandwidth allocation algorithm of EPON. Therefore, aiming at the uplink channel access of EPON, people have put forward various dynamic bandwidth allocation algorithms, but most of them belong to intensive algorithm, ie the distributed bandwidth allocation (DBA) algorithm runs in OLT which is the interceder to allocate the uplink transmission time slot for ONU. A new distributed dynamic bandwidth allocation algorithm (DDBA) is proposed in this article, in which ONU decides the size of transmission window based on the assistant information transmitted by OLT and self queue length. The simulation result indicates that comparing with IPACT (Interleaved Poling with Adaptive Cycle Time)(G. Kramer, 2002, P. 89-107), under the high network load, DDBA could obviously improve the average end-to-end time delay and the average queue length.