It is generally regarded that relaxing farmers’ financing constraint is an important measure to increase the farmers’ income. Rural financial reform in Guangxi province provides a natural experiment for the view that relaxing the financing constraints is to increase farmers’ income. In this paper, we use the data from 13 reformed counties and 60 non-reformed counties in Guangxi province, through propensity score matching method to eliminate selectivity bias, we estimate the average impact on farmers’ income from the rural financial reform. The results show that farmers’ income increase effect is embodied after two years of reform, that in 2012 and in 2013, the farmers in the reformed counties averagely increase pure income 227.86 yuan and 270.26 yuan more than the farmers in non-reformed counties, that the farmers’ income increase effect after relaxing financial constraint has regional difference, the more developed and the more rich the areas are, the more significant the role is, which reveal that the farmers’ income increase effect after relaxing financial constraint is restricted by farmers’ financing demand. Therefore, the farmers’ effectively financing demand should actively be raised while rural financial reform is deepened and financing constraint is relaxed.