Abstract: Under the dual pressures of anthropogenic activities and climate changes, various ecological disasters degrading generally typical ecosystems of marine living resources occur frequently in China. The situation of marine ecological security is facing with challenges of urgent requirement of marine ecological monitoring as the existing traditional monitoring techniques having disadvantages of low frequency monitoring, limit data storage and inability of trend analysis hardly meeting the needs of ecological monitoring. Marine ecological on-line monitoring technology has the characteristics of real-time, all weather and continuity of data obtaining during the monitoring performance. Thus, it can follow the information changes of environmental quality timely and accurately. It has incomparable advantages over traditional monitoring methods. In this paper, different levels of comprehensive on-line monitoring system, monitoring platform and on-line monitoring sensors/analytical instruments, the status of ecological on-line monitoring technology home and abroad are fully analyzed. At last, the problems of marine ecological monitoring in China are discussed and the corresponding development suggestions are put forward for the development of ecological monitoring in China.