The stability of SnS at high pressure is studied using a constant pressure ab wino technique. For the first time, a pressure-induced phase transformation from the Prima structure to a Cmcm structure with the application of pressure is predicted through the simulations in this material The Cmcm phase is still a layered structure, consisting of rocksalt-like bilayers, similar to that formed at high temperatures. The Cmcm structure is fivefold coordinated This phase transformation gradually proceeds and is due to the significant decrease of the second neighbor distances. This phase change is also studied by total energy calculations. (C) 2010 Elsevier Ltd All rights reserved.