Abstract: A bottom-supported submersible buoyant system is designed for long-term seabed environmental monitoring in a natural gas hydrate area. It can be used to study the characteristics of submarine environment in the area and to collect long-term environmental parameters for seabed boundary layers. Through comparison of related parameters acquired before and after, the changes near seafloor resulted from the exploration and pilot production of natural gas hydrate could be monitored and assessed, for the purpose to reduce the risk of environmental changes. The submersible may carry various sensors, such as those for measurement of methane and carbon dioxide, CTD (Conductance, Temperature and Depth), dissolved oxygen, turbidity, transmittance, ADCP (Acoustic Doppler Current Profilers) and single-point RCM (Recording Current Meter). It can be recovered by discarding the clump weight through deep-sea acoustic release transponder. The maximum working depth of this system is 4000 meters and the batteries are sufficient to provide power for all the sensors for more than 180 days. After a successful deep-sea test with effective data and safe recovery in northern South China Sea, it is confirmed that the bottom-supported submersible buoyant system has a promising prospect of application in improving safe and effective use of natural gas hydrate resources.