The research on Ｒ2 has grown fast in the past decades． Ｒ2 has evolved from a purely econometric symbol to a variable of stock price synchronicity，and is linked to firm-specific information content． Scholars explore the causes，consequences，and the generating mechanism behind the Ｒ2 from the law and finance the-ory，principal-agent theory，asymmetric information theory，corporate governance theory，and many other per-spectives． The paper first reviews the causality association between asset pricing model，Ｒ2 ，and the stock price synchronicity，and then presents the findings on the causes and consequences of Ｒ2 ． After that the paper discusses the academic debate on Ｒ2 ． Based on the above，this paper looks forward to the future researches from the two aspects: the source of Ｒ2 ，and the potential effects of culture and politics on Ｒ2 ．