In view of the problem of clean power consumption of berthing ships and rapid response to power supply of some ports, small islands and offshore platforms, on the basis of describing the development status and main systems of large-scale LNG generating ships, and referring to the relevant design experience of LNG ships at home and abroad, the modular design method is adopted to carry out the scheme design for the core contents of a 20MW LNG generating ship, such as the ship hull, LNG pipeline system and power propulsion composite system, which provides an alternative solution to the main difficult problems of the design of this kind of ship.