With the rapid development of Internet technology, there have been many new services which require high bandwidth. EPON (Ethernet Passive Optical Network) has become one of the best technologies in the next generation broadband access network because of their high-bandwidth and low-cost. Dynamic bandwidth allocation (DBA) is one of the most critical issues in EPON network. In this paper, a new DBA algorithm is proposed to support QoS and to get higher performance. The proposed algorithm could avoid bandwidth wastes result from dynamically allocation from differentiated services and unused bandwidth. Detailed simulations are performed to verify the effectiveness of the proposed DBA algorithm.