In order to study the unsaturated infiltration characteristics of yellow cotton soil containing spherical microplastics with different content and different particle size under rainfall conditions, a set of model test equipment for soil column vertical infiltration under simulated rainfall conditions was developed. Seven sets of rainfall infiltration tests were carried out on the yellow cotton soil. The result shows: (1) When the rainfall intensity is 20 mm/h, the microplastic particle size is 5 μmand the microplastic content is 0.05 %, rainwater infiltration is promoted, and the content of other microplastics prevents rainwater infiltration, and as the content of microplastics increases, the water point and saturation point appear earlier. (2) When the rainfall intensity is 20 mm/h, the content of microplastics is 0.25 % and the particle size of the microplastics is 3 μm, the infiltration of rainwater will be significantly promoted, and no water will be generated during the whole test period. When the particle size of the microplastics is 5μm and 8μm, a lot of water will be generated, which will block the infiltration of rainwater. (3) The hydrophobic effect of microplastics significantly affects the process of rainwater infiltration, but its impact on the peak water content is relatively weak. However, its impact on the peak water content is relatively weak, the peak water content gradually decreases with the increase of the microplastic content, and gradually increases with the increase of the microplastic particle size.