Based on data from Urban Household Survey (2009), this paper analyzes the regional income gap among urban residents from the perspective of hierarchy of cities. The main findings include: large income gap exists among residents in cities of different hierarchical levels, and the hierarchical gap among cities amounts to about 11% of the overall gap, larger than the hierarchical gap among the three major economic regions (eastern, central and western); regression analysis shows that hierarchy of cities plays an important and significant role in income determination, even when other variables that affect income are controlled. The impact of hierarchy of cities on income gap is different on the different quantiles on income distribution. Generally speaking, the importance of hierarchy of cities increases as the quantile of income distribution get higher, yet at the highest quantile, its importance decreases. Furthermore, this paper decomposes the income gap among cities of different hierarchical levels in terms of mean value and relevant quantiles. Generally speaking, the income gap among cities of different hierarchical levels is caused by the disparity of income determination mechanism (coefficient), especially by the constant term; on the contrary. The impact of the variables representing characteristics of different populations is relatively low, and this fact is reflected when the income determination mechanism shows fragmentation among cities of different hierarchical levels.