Abstract: Methods of lateral scanning sonar, sub-bottom profiler and echo sounding measurer were used together to survey a living oyster reef ecology system in the shallow sea area of Dashentang in Tianjin City, which always submerge under sea water. In this paper, we aimed to provide detailed investigation data for protection of this living reefs. The investigation results show that the reefs are composed of three separated sub-reefs. The total area of the reefs is only about 3km2, with maximum thickness of 1.2m and average thickness of 0.6m. Water depth (from average sea level to the bottom) of the investigated area ranges from 3.4 to 5.6m. There is only about 1m elevation fluctuation locally in some area where there is reef surface developed. This living oyster reefs should be protected and recovered in order to keep the diversity of ecological resources.