The data flow characteristics in downstream transmission of Ethernet Passive Optical Network (EPON),which is integrated with burst access mode,are analyzed in this paper,and a downstream transmission scheme based on optical burst switching is proposed hereby.The bursting arrival of data frames from Optical Line Terminal (OLT) will fully occupy the downlink bandwidth,thus delay the transmission of data frame with higher priority,and overload the Optical Network Unit (ONU).The influences of burst arriving data frames on the transmission of higher-priority data frames can be reduced through scheduling the downlink bandwidth resources based on priority.The sliding windows are used to regulate the arrival rate of each ONU data frame to relieve the overload of ONU processing.The transmission scheme is simulated and evaluated on OPNET Modeler.The results verify the feasibility of the scheme.