Abstract:  The developments of subsea mechanical trenchers are summarized. Most of the mechanical trenchers are made by SMD and IHC. There are 3 kinds of mechanical trenchers including pipe trencher, cable trencher and multi-functional trencher. They used chain and cutters to trench, and equipped with track chassis. Most of the trenchers are equipped with jetting module and suction module, which make them high efficiency. The mechanical trenchers are now multi-functional suitable to all geotechnical conditions, and modular designed.