The present invention relates to a method for realizing automatic work unit in EPON which comprises procedures of OLT networking, ONU electrify automatic warrant/configuration, ONU networking, HG networking, speech port activation, disassembly, speech port deactivation, process of ONU port connecting equipment changing, and ONU replacing. The invention also provides a system of realizing automatic work unit in EPON. Workload of network maintenance center staff can be reduced effectively, and business establishment efficiency can be improved through the invention. Meanwhile, ONU automatic discovery, authorization and networking, automatic acquisition of configuration, automatic recognition of ONU externally hanging household gateway apparatus, ONU disassembly, household gateway disassembly, ONU cleft grafting, log management, and functional failure management can be realized through the method.