There are a lot of researches on income gap, but these researches do not make deep studies from the angle of natural income gap. Natural income gap is used as the utmost limit value of gapnarrowed convergence to set up the related analysis model and to analyze the variables to form income gap in order to reveal the relationship among effective resources flowing, comparative advantage and income gap. If the effective resources are not flowing in time or do not flow, the economic body can not transform the effective resources into comparative advantage, under the condition of that comparative advantage is not sufficiently brought into fully play, however, each economic body can not form equilibrium state which has competence so that economic efficiency is decreased and income gap is more and more away from natural income gap. Thus, the enlargement of the income gap results from insufficient flowing of the effective resources, the key to narrowing the gap lies in making and perfecting all kinds of soft and hard measures to promote the flowing of the effective resources, and the income gap will converge to natural income gap under the condition of continuous and sufficient flowing of the effective resources.