For more efficient air-conditioning in large scaled vessels, structure of air inlet room and location of supply fan are very important. In this study, we have modeled an air intake room of large scaled vessels and tried to examine surrounding flow characteristics around supply fan by a numerical simulation using computational fluid dynamics based on three dimensional steady-state Navier-Stokes equation and standard k-ε model. A commercial CFD program, FLUENT, is used on the analysis. Finally, the analysis showed that the supply fan should be located at the inner side rather than outer side of air intake room, which was original design