When dump trucks unload dusty materials, dust particles with a diameter of 1 to 75 microns slide out of the dump body and float into the air. Dust particles naturally settle down spending a few hours, which causes air pollution. People who work in this environment daily suffer serious physical harm. To study the movement of dust particles during the unloading process, a scaled-down model is used to simulate the process of dump truck unloading gravel, and a high frame rate camera is used to record the movement trajectory of dust particles during the unloading process. In this paper, by observing the movement process of unloading dust particles by dump trucks, based on the principle of dynamics, a mathematical model describing the unloading of dust particles in the dump body and a mathematical model of the diffusion of dust particles in the air are established. Take the small gravel sampled at the construction site as an example of the experiment. Image processing is performed on the test video to obtain the position of the dust particles unloaded by the body and the movement data during the diffusion process. The longitudinal position of the dust particles unloaded by the body is compared with the analysis results of the mathematical model, and the mathematical model that describes the dust particles being unloaded by the dump body is improved. Sensitivity analysis of the size parameters of the dump body is carried out using the dust particle unloading model. Substituting the movement data of dust particles in the air into the dust particle diffusion model and solving the movement viscosity coefficient of the gravel particles. The experimental data and mathematical models in this article will provide a certain reference for researchers who study the movement of dust particles and dust collection in engineering.