Ethernet Passive Optical Network (EPON), which represents the convergence of low-cost Ethernet equipment and reliable fiber infrastructure, appears to be the best candidate for the next-generation broadband access network. A coin has two sides. Although EPON inherits the benefits of Ethernet, it also suffers some disadvantages. With its origin as a LAN technology, where “best effort” delivery and 99.96% uptime were acceptable, Ethernet was never considered to be a candidate for achieving “carrier-class” status, mainly because lack of powerful OAM capabilities. That’s to say OAM function is essential to carrier-class EPON. In this study, the principals of EPON and OAM, together with the necessity of OAM, are presented firstly. Besides, different ways to provide OAM in ITU-T APON, GPON are analyzed respectively. Three means to obtain EPON OAM, using MAC Control Frame, Physical Link Service Overhead Coding Sublayer (PLSOCS) and Reconciliation Sublayer (RS) Preamble are proposed in detail. Moreover, the main functions, such as remote failure indication, remote loop-back, link monitoring and variable retrieval are studied subsequently. After that, the concrete implementation of OAM in EPON is addressed, combining with hardware and software. As a result, an effective way to carry out EPON OAM can be easily drawn.