Abstract: The requirements of vacuum systems, such as semiconductor lithography and electric vacuum devices, are not only limited to vacuum degree, but also put forward higher requirements for cleanliness. The research shows that some components of the vacuum system will produce particle contaminations, which can pollute the vacuum environment under certain conditions. Therefore, it is necessary to study the transport law and distribution of the particulate matter in a vacuum pipeline and provide the theoretical basis for the particle contamination protection method. In this paper, the transport law of particle contamination under different gas flow patterns was simulated via the COMSOL software. In the simulation, the forces applied to the particle contaminations mainly include gravity, drag force and lift force. The effects of pressure, pumping speed and particle diameter on the gas flow and particle transport characteristics were studied. The results show that the drag force of gas flow on particles is dominant in the transport characteristics of particles under different conditions. When the pressure and particle diameter are constant, the increase in pumping speed enhances the probability of particle deposition at the pipeline outlet or even direct particle transport to the outlet through the gas flow. When the pressure and pumping rate are constant, the smaller the particle diameter is, the easier it is to reach the outlet with the gas flow. When the particle diameter and pumping speed are constant, the particle transport trajectory changes correspondingly with the variation of pressure.