Abstract Submerged combustion vaporizer (SCV) is a type of liquefied natural gas (LNG) vaporizer which utilizes the combustion heat from the produced natural gas (NG) or boil-off gas (BOG). Because of its compact structure and quick start-up ability, SCV is widely equipped among the world's LNG receiving terminals. In this paper, the operation characteristics of a typical SCV are simulated numerically. The curves of LNG temperature and heat transfer coefficient along the heat transfer tube under the rated condition are calculated and analyzed. The water bath temperature, which is one of the key operation parameters of SCV, is analyzed to evaluate the performance under off-design conditions. It decreases with LNG inlet temperature, and increases with LNG mass flow rate and tube fouling resistance. However, it has little relation with LNG inlet pressure. The minimum heat load, a special issue of SCV to avoid freezing in the bath, is discussed in the end.