This paper presents an analysis and simulation method for ONT Management Control Interface(OMCI) protocol in the GPON equipment development and interoperability tests.This method extends the existence range of OMCI messages so that the OMCI messages received at an Ethernet port of ONU can be processed by an analysis computer connected to the port.It is proved that this method can rapidly parses the message contents and forwarding process and thus provides an effective means for their accurate location.