One of the most important purposes of active fault detection is to evaluate the seismic risk of active fault on detection result. A large number of facts show that the blind active faults in eastern China have the capability of earthquakes with MS≥7.0. During the active faults detection work in Songyuan，we found an active fault，which was called the Gudian fault. In this article，detailed underground structure of the fault is obtained through 3D seismic data. The latest activities and sliding rate are obtained from the shallow seismic exploration and the terrace borehole work. On the basis of comprehensive study on the geological structure，the quaternary activity，historical earthquakes and earthquake activities of the fault，we evaluate the potential maximum earthquake magnitude on subsurface fracture parameters，and confirm that the fault has been active since late Pleistocene，with the ability of earthquakes with MS7.0. In addition，the recurrence period or the annual rate is calculated by seismic moment ways. The historical earthquake recurrence probability model of Chinese mainland is adopted to calculate the occurrence probability of the Gudian fault in the coming 50～200 years.