Abstract: Unlike continental landslides, underwater landslides are hard to be observed due to the specific hydrodynamic conditions. So far there have been no standards and guidelines available for the procedures on disaster-causing mechanism studies and instability assessment, which involves not only the in-depth study of seabed instability, but also the formation and evolution of buttle and abyss, deep sea project development, business interests, marine geological disaster forecast, safety of the marine engineering and constructions, and other problems. With the rapid progress in China's marine scientific survey and various submarine projects, great achievements have been made by China in the past decades, in particular in the following three aspects: marine geological survey, disaster mechanism analysis and instability assessment. By integrating geophysical, in-situ seabed monitoring, numerical simulation, physical experiment simulation and other techniques, a complete process from early investigation to late evaluation is preliminarily presented in this paper, which is critical important for seabed stability assessment indeed.