Side exhaust system is an exhaust system configuration which is suitable for small ships that cannot install exhaust pipe due to the limited space arrangement. It can be characterized of the high flexibility, aesthetics and stealthiness. There are many factors involved in the design of this exhaust system. The current study carries out the simulation of this exhaust system from the arrangement and back pressure of exhaust pipes, and provides suggestions for the preliminary design. This article simulated the back pressure and arrangement for the design, and provided some advice of the preliminary design.