The geological storage of carbon dioxide (CO₂) is a promising technology for the reduction of greenhouse gas emissions. There are 8 operating largescale integrated CCS projects (LSIPs) and 74 LSIPs in different stages all over the world. CO₂ injection may increase the formation pressure, and CO₂ leakage from natural and manmade pathways may affect human health and ecosystems. In order to provide assurance that suitable sites can be selected and can be operated safely, sequestered CO₂ will need to be monitored to verify that there is no leakage and to provide confidence in predictions about its future behavior over the long term. A review of the CO₂ geological storage monitoring all over the world is presented, including the regulations, guidelines and the application of technologies in different projects. The objects and technologies of baseline monitoring and routine monitoring technologies of onshore and offshore CCS projects (SECARB, Otway, Lacq, Weyburn, Gorgon, Sleipner, In Salah, Snhvit, CO₂SINK, RECOPOL) with different reservoir types (deep saline formation, oil field, depleted gas field and depleted coal bed) are investigated and analyzed in detail. Moreover, a monitoring selection tool (MST) is introduced and applied to the Shengli Oilfield CO₂-EOR project. According to the analysis of monitoring database and evaluation results of MST, the potential baseline monitoring objectives and technologies of the Shengli Oilfield CCUS project are proposed. Finally, outline and methodology of the monitoring work are discussed briefly.