中文摘要：

2014年中国基尼系数是0．469，处于较高位置。个人所得税是缩小收入差距的常见措施之一。其基本原理是高、低收入者分别适用高、低边际税率，高收入者的单位收入税负高于低收入者的相应值，因此全社会的税后收入差距小于税前收入差距。个税收入调节功能的发挥依赖于四个要素——免征额、最低边际税率、最高边际税率、最高边际税率适用的收入最低限额。笔者构建高、低收入者的两群体个税模型，研究四要素对收入差距的影响，发现了四要素与收入差距关系的八个推论，且上述推论基本符合跨国截面数据模型的实证检验结果。研究显示，中国要加强个税的收入调节功能，需要提高最低、最高边际税率，降低免征额与最高边际税率适用的收入最低限额。依据上述原则，本文制定了新的七级超额累进税率表。

英文摘要：

In 2014, China＇s Gini coefficient was 0. 469, and this value was relatively high. Individual Income Tax is a common measure to narrow income gap. The fundamental theory is that high and low income group are taxed by high and low marginal rate respectively. The tax burden per unit of income for high income group is larger than that for low income group, so after-tax income gap is lower than pre-tax income gap. Redistribution function of Individual Income Tax is based on 4 elements, such as Tax Exemption Amount （TEA）, Bottom Marginal Rate （BMR）, Top Marginal Marginal Rate （TMR） and Minimum Income Amount of Top Rate （MIA） . Two-group individual income tax model was built to study the effects of such 4 elements on income gap. 8 inferences inferred by the model were proved by the results of the international crosssection data model. In order to strengthen the redistribution function of Individual Income Tax, BMR and TMR should ble was be raised, while TEA and MIA should be reduced. Finally, a new 7-level extra progressive tax rate tadrawn up.