The Data analysis of national 1978-2013time series and 1978-2014time series in Guizhou both show that the expenditure of national rural public service has positive effect to relieve poverty. Meanwhile, regression analysis based on factor analysis of the field survey data in 10 poor villages in Guizhou shows that the higher the satisfaction degree of farmers to the local public service supply is, the higher the level of their income is, which indirectly reflects the poverty relieving function of the rural public service expenditure. In view of the backward rural public service level in Guizhou, it is necessary for the government to make an overall plan, elevate famers’ satisfaction level and speed up the infrastructure construction so as to better the public services, farmers’ subjectivity, local culture and supporting facility in poor rural areas. In addition, qualified environmental condition, internal condition and guarantee condition serve to amplify the poverty relieving function of rural public service expenditure in Guizhou.