Abstract: With consideration to non-synchronization of clocks in production supervision systems at stations along PetroChina's long-distance oil and gas pipelines, 8 clock synchronization technologies in two categories, together with inservice devices and system framework of production supervision systems have been analyzed and summarized. In addition, NTP, GPS, Beidou, Modbus and CIP technologies have been reviewed to clarify methods for clock synchronization and insertion of time label in PLC data for the SCADA system, leakage monitoring system, video monitoring system, voice phone system, third party equipment and other production monitoring systems that may require time-synchronization. In addition, the synchronization scheme have been proposed for the control center, subsidiary control centers, stations and valve chambers along the pipelines. The proposed scheme has been deployed in multiple stations along the Mohe-Daqing Crude Oil Pipeline to synchronize clocks in production supervision systems. With time label inserted in data uploaded from PLC, time sequence of events can be reflected accurately to provide necessary guarantee for accurate analyses of production activities and relevant events.