Abstract: The Northern Depression of Beibuwan basin experienced multi-stage tectonic movement in paleogene,resulting in strong basin reformation.From the present tectonic framework,by denudation restoration,together with analysis of the characteristics of fault activities,prototype structure reconstruction has been conducted and basin formation mechanisms in paleogene in the northern depression of Beibuwan basin are discussed in this paper.It is believed that the subsidence and depocenters of Northern Depression shifted from west to east and from north to south.In Middle Eocene during deposition period of Liushagang formation,Weixinan D sag and Haizhong west depression were the same sedimentary unit.Faulting and uplifting controlled the basic shape of depressions,especially the uplifting activity of Weixinan low in Northern Depression,which play a key role for partition of unified lake basin in paleogene.