The abnormal behave of IPO, and especially the excess earnings on the first day of IPO is always a hot research issue. Concerning this issue, researchers study from two aspects:"first-market underpricing" and "second-market overvaluation". There are imperfactions in both, the former one contradicts with IPO's long-term performance, and the latter lacks theoretical basis. So there is room for further research. This paper, centering on the potential influencing factors for the excess earnings on the first day of IPO, discusses whether theses factors have influences on IPO's abnormal behave the first day; and how and to what extent the influence is; and the differences between theses factors. It further analyzes the influencing factors, and gives suggestion for the development of securities market in our country.