Marine carbon geological sequestration is crucial for achieving carbon peaking and carbon neutralization in China. However, there exist risks of carbon dioxide (CO₂) leakage that leads to seabed geological disasters, severely threatening the safety of marine engineering. Therefore, it is of great practical significance to monitor the environmental geology of sequestration areas. This study briefly introduces several demonstration cases of marine carbon geological sequestration and explores the disaster mechanism associated with CO₂ leakage in seabed sequestration areas. It also sorts out the marine environment monitoring technologies in typical CO₂ controlled release tests via examples and analyzes the environmental geology monitoring technologies related to CO₂ leakage, including seismic investigation and monitoring, resistivity monitoring, gravity monitoring, seabed deformation monitoring, and sediment pore pressure monitoring. Moreover, the prospects of China's marine carbon geological sequestration and its environmental geology monitoring are presented. We suggest that long-time, low-cost, and real-time monitoring technologies should be developed, a systematic and intelligent multi-dimensional disaster identification model should be established in combination with the baseline investigation of the sequestration areas, and a multi-faceted, multi-level, and multi-disaster monitoring and forecasting system should be built.