The factors influencing huge divisions of wealth in society are widely studied by researchers. However, with the rapid development of the Internet, whether polarization or equalization of market shares exists in e-market among sellers springing up online, and how e-commerce affects its formation is still unknown to us. With a seller sample retrieved from Taobao, our study examines the polarization phenomenon and explores the determinants of its formation in the context of online markets. The descriptive analysis suggests a polarized phenomenon exists in e-commerce. Then this study applies quantile regression approach to investigate the factors that influence the formation of polarization in C2C mobile phone market. The results indicate that, a polarized sales distribution is existed; reputation and negative ratio play more important roles, while the number of items has a lower influence gradually. The empirical results can help us find the reason of polarization in C2C e-market.