[Objective] In order to avoid the pollution of the ship's smoke on the deck and the air intake, and to protect the crew's living environment and working environment, and further analyze the smoke diffusion characteristics. [Methods] First, a smoke diffusion model was established using computational fluid dynamics (CFD) methods, and statistical performance indicators were introduced for evaluation to verify the accuracy of the model. On this basis, the effect of flue gas release temperature on the diffusion process of ship smoke in a calm wind environment was studied, in order to understand the mechanism of the process of smoke deposition and diffusion; and the effect of smoke on the ship's air inlet was further analyzed. [Results] The results show that the release temperature will determine the transition process of flue gas from heavy gas cloud to neutral gas cloud, thereby determining the diffusion/sedimentation effect. As the temperature increases, the pollution degree to the ship's air inlet is smaller; as the flue gas diffuses vertically in calm weather, the pollution is concentrated in the middle of the ship; When the release temperature reaches 423K, the flue gas will not significantly settle and will directly diffuse into the normal temperature environment. [Conclusion] The study clarified the diffusion process of ship smoke under calm weather and the effect of release temperature, and the results can provide a theoretical basis for the design of ship exhaust parameters and the layout of air intakes.