Poverty eradication is a common goal of human society and a worldwide problem. At present, China has entered the decisive stage of poverty alleviation and the key period of urbanrural linkage poverty alleviation, so it is of great academic value and practical significance to study urban poverty reduction. Taking 8 provinces and regions in the west of China as research samples, this paper makes a systematic analysis of the urban poverty reduction effect of transportation infrastructure and its transmission mechanism. It is found that the improvement of road and railway mileage and its density in western ethnic areas will significantly reduce the absolute poverty and relative poverty of towns. Compared with railway traffic, the urban poverty reduction effect brought by road traffic infrastructure construction is more significant, and compared with transportation mileage, the poverty reduction effect of transportation density improvement is more worthy of attention. Further mechanism analysis shows that at this stage, transportation infrastructure construction in the western minority areas mainly promotes urban poverty reduction through the mechanism of promoting population flow, and the promotion mechanism of commodity flow is likely to worsen the urban poverty in the areas. In order to give full play to the urban poverty reduction effect of transportation infrastructure construction, it is necessary to focus on promoting the internal and external connection and network construction of transportation infrastructure, give priority to the development of road transportation services closely related to the flow of urban poor people, continuously enhance market access, and improve the transportation accessibility of ordinary people.