Abstract: Human engineering activities under the sea, such as the exploitation of deep-water oil and gas, the trial production of marine gas hydrates, and the construction of submarine pipelines, are rapidly increasing with time. They have attracted great attention from the geosociety since deep-sea geohazards often occur with those submarine resource extraction and engineering activities. Landslide is a kind of geohazard often happened in the deep sea, so the instability study of deep-sea landslides has become an important subject of marine scientific research. This paper is devoted to the research status and progress of deep-sea landslides both at home and abroad, and the morphological classification as well as research methods and means. The effects of earthquake, fault activity and gas hydrate decomposition on the instability of deep-sea slopes are discussed. In the past decade, with the emergence of some new research methods, the research focus of deep-sea landslide has shifted from the morphological classification to the trigger mechanisms and in-situ observation of deep-sea landslides. However, field investigation, physical simulation and numerical simulation still remain as the main means for the study of deep-sea landslides, and unconventional techniques, such as ROV/HOV are also gradually applied. Deep-sea landslides are usually caused by joint internal and external geological and hydrodynamic factors. The coupling effect of trigger mechanisms and the impact of new trigger mechanisms are still the focuses for future researches.