Abstract: The urban-rural income gap has become a major risk of China’s economic and social sustainable development. How to narrow the income gap and achieve social justice becomes the core issue of China’s development, as well as academic research hot spot. Applying the Theil index and its decomposition, EDSA-GIS, mathematical statistical, this study analyzed the characteristics of the time evolution, spatial differentiation pattern and influencing factors of income gaps of 19 counties in Ningxia from 1990 to 2013. Results show that: 1) the overall income gap of Ningxia and urban-rural income gap was increasing with fluctuations, but the urban and rural income gap was decreasing with fluctuations. The overall income gap was mainly caused by the urban-rural income gap; 2) Ningxia urban-rural income gap showed significant spatial difference with “high in the North and low in the South”, while urban-rural income ratio showed “low in the North and high in the South”; 3) the hot spots located in the South and cold spot in the North since 1990, presenting of spatial cluster and significant space dual structure; and 4) the improvement of industrialization level and per capita GDP will widen the urban-rural income gap, while the improvement of citizenization and financial support for agriculture will narrow the urban-rural income gap. This paper also suggests to increase the support for the economic development of the Central and Southern regions, to establish the new socialism countryside and beautiful villages, to increase finance support for agriculture to narrow the urban-rural income gap and promote coordinated development.