Abstract: Based on the field statistical data from oilfields such as Honggang, Jilin; Lamadian, Daqing; Erlian, Huabei, it is concluded that the daily incremental oil percentage of the fractured well is normally distributed together with the formation pressure. The optimal pressure for fracturing is near the formation pressure. This paper explores its mechanism, analyzes and discusses some field methods for evaluating the pre-fracturing formation pressure, and hopes can provide reference and aid for fracturing work at home.