By using FLUENT software, this paper constructed three-dimensional mathematical and physical model that describe the combustion process in swirl chamber S195 of the single-cylinder diesel engine. The numerical simulation and analysis were carried out to obtain the gas' movement in the swirl chamber, such as the gas' changes in pressure, temperature and the situation of soot emission. Furthermore, the experimental results indicated that the model could exactly simulate the combustion process at the diesel engine's swirl chamber.