With the emergence of Ethernet as a convergence layer in access network, Ethernet Passive Optical Network (EPON) has evolved. It is being considered as a promising solution to the 'last mile' problem in next-generation broadband access network. An EPON is a point-to-multipoint tree topology, which carries 802.3 Ethernet frames between an optical line terminal (OLT) and multiple optical network units (ONUs) via a passive optical splitter. The multi-point control protocol (MPCP) for medium access control (MAC) in an EPON. In this paper, we investigate design issues for access networks based on passive optical network technology, and we present a preemptive transmission mechanism that works on MAC and PHY layer of OLT and ONU components. We conduct detailed simulation experiments to study the performance and validate the effectiveness. The proposed novel scheme effectively reduces the frame queuing delay as well as jitter, so as to enhance system throughput.