The invention provides an LNG single-fuel ship and belongs to the technical field of ship 
engineering. According to the structure of the LNG single-fuel ship, a hole is formed in a main 
deck of a 
storage tank cabin, the 
storage tank cabin is designed to be of a sunken structure, one part of a gas 
storage tank is located above the main 
deck, the other part of the gas storage tank is located below the main 
deck, a double-wall 
pipe in an 
engine room is adopted as a 
fuel gas delivery 
pipe, a rectangular ventilation guide 
pipe is arranged on the periphery of the 
tail segment, close to an engine, of the 
fuel gas delivery pipe, and a round ventilation guide pipe is arranged on the periphery of the segment, on the upstream of the rectangular ventilation guide pipe, of the 
fuel gas delivery pipe; a liquid outlet pipe on the downstream of a flowmeter is divided into a main path and an auxiliary path, wherein the main path is finally connected to a mixer, and the auxiliary path is connected to the portion, between a second-stage pressure reducing valve and a downstream manual drainage pipe, of the main path through a fault opening type electromagnetic 
pneumatic valve and an auxiliary path 
safety valve; the mixer is connected with a 
supercharger, and the 
supercharger is connected with the fuel gas delivery pipe. Due to the design, the strength and the stability of the LNG single-fuel ship are improved; fuel adding, fuel feeding and safety protection are achieved, and the safety of a ship power 
system is guaranteed.