The present disclosure provides a method, apparatus and system for transmitting OMCI messages. The method includes receiving an OMCI message from a cloud server, wherein the cloud server supports vOMCI; judging whether the received OMCI message is associated with device information of the optical line terminal, if so, obtaining device association information corresponding to the received OMCI message, filling the device association information into the received OMCI message, and sending the filled OMCI message to the optical network terminal, otherwise, sending the received OMCI message directly to the optical network terminal.