Abstract: With the rapid economic development and the continuous improvement of people's living standards, exhaust emissions and PM2.5 pollution caused by automobiles have gradually attracted widespread attention. Monitoring air pollution and assessing the quality of air have become one of the essential performance features of automobiles. Construct a coupling model based on mie scattering principle and CFD-DPM for the detection of dust particles in vehicle-mounted PM2.5 sensors. Four different particle sizes of dust were selected to conduct numerical simulation on the influence of factors such as the height of the rising edge section corresponding to the receiving area of the photosensitive element, the presence or absence of the flow guide grid structure, and the fan speed on the scattering reception. The results show that setting the rising edge cross-section h=1. 4mm, constructing the deflector grid structure and the high fan speed are more conducive to capturing dust particles. The research provides certain theoretical support for the structural optimization of vehicle-mounted PM2.5 sensors.