Abstract: Exploitation of methane hydrate, which is originally stored in deep-sea marine deposits, will deteriorate the mechanical properties of the deposits and therefore lead to seabed instability, such as submarine landslide. A few essential issues associated with methane-hydrate-related seabed instability as well as the limitation of existing analysis methods are highlighted. A new methodology is proposed based on the theory of micro-to-macro geomechanics, which uses the discrete element method to bridge the microscopic characteristics of geo-materials with methane hydrate and their constitutive behaviors in macro sense.