A M5.7 earthquake occurred between Ruichang and Jiujiang in Nov.26

2005.Its epicential intensity was greater then 7.Then the earthquake engineering parameters at the outlet of Boyanghu Lake were checked.The seismotectonic of Ruichang earthquake and after-shock-tend was analyzed at first.A potential earthquake risk zone was shaped based on analyzing earthquake background and seismic activity around the outlet of Boyanghu Lake.Because the seismotectonic of Ruichang earthquake is about 40 km away from the outlet

the earthquake engineering parameters at the outlet basically do not change.The process of the work provides a model for post-earthqake reconstruction.