Abstract: By employing the method of parameters and semi-parametric quantile regression, this paper makes an empirical study on the Kuznets curve with the research objects of 80 municipalities and prefecture-level cities of China to reveal the complicated non-linear relationship existing between China’s economic development and income gap. The results of the parametric and quantile regression show that there is a“U-type”curve relationship at the lower- middle quantile site, rejecting the“inverted U”hypothesis; while the results of the semi-parametric quantile regression show that at the lower-middle quantile site, the Kuznets curve displays the characteristics of“U-type”，but at the higher quantile site, it displays the characteristics of a“W-type”，presenting the connection between two“U-type”curves. In addition, this study chooses the two income inequality indicators, i.e.. Theil index and the income share taken by the most affluent 50% of the population, to carry out a robustness test, the results indicate that the outcome of the analysis of these two income gap indicators coincides with the outcome of the analysis which takes Gini coefficient as the income inequality indicators.

Key words: Kuznets Curve; income gap; quantile regression