By integrating the working principles of water silencers with the pipeline system and water cabin characteristics of underwater vehicles, a gas-water cabin silencing method was proposed. Air with certain pressure and volume was filled into the water cabin to form an accumulator-type elastic-compressive expansion chamber silencing cavity, and the water cabin of the underwater vehicle was fully utilized to silence the sea pipeline. Experimental studies were conducted on the silencing principles and performance of the gas-water cabin. The results show that the flow and pressure pulsation at the pipeline outlet is effectively suppressed by the gas-water cabin, the noise propagation pathway of the pipeline is blocked and the underwater radiation noise of the pipeline system is reduced. This gas-water cabin provides a usefully approach on underwater radiation noise reduction of underwater vehicle.