The factors influencing urban-rural income gap are decomposed into opening-up degree, education development level, economic development level, marketization progress and urbanization process, the panel data of 31 provinces and municipalities during 2005-2015 are used to make the Shapley value decomposition, and the results show that economic development, marketization and urbanization have bigger contribution to urban-rural income gap, however, opening-up, education development and financial development have smaller contribution to the gap. The linear regression analysis indicates that the enlargement of opening-up, deepening the market-oriented reform, accelerating financial and economic development and boosting the urbanization are conducive to narrowing the income gap. The analysis of threshold effect model by further using the level of economic development as the threshold variable indicates that the effect of economic development on the urban-rural income gap shows an inverted U shape curve, furthermore, the higher the economic development level is, the bigger the effect of education development, financial development, economic development, marketization and urbanization and so on on the action narrowing the income gap is. Thus, in the process of narrowing the rural-urban income gap, China must accelerate the economic development, opening-up, financial development, marketization and urbanization for the less-developed areas.