Abstract: The studied area is the northern part of Hebei province, including Beijing-Tianjin region and some regions in Shansi prevince and the Inner Mongolia Autonomous Region.29 seismic stations were selected in this area and 6 selected in the east-extending background area.By the body wave of deep focus distant earthquakes from those stations and by selecting the medium strucgure medel, the theoretical seismograms were calculated,which were fitted with the observed seismograms so as to define an acceptable model for the medium structures under the seismic stations.In titting,for each seismic station,the body wave recordings of deep focus distant earthquakes were selected for several times to be as observed seismograms.Urually,for each seosmic station,the theoretical seismograms of 60 different models were calculated.In fact,the obtained result is deeper than the crust,being the medium structure of upper mantle of the crust in the depth of about 80 kms (that is, roughly corresponding to the lithostrome or called lithosphere),they all consist of about 10 layers of media.By wave form fitting, the medium stratified structures of the mantle under above mentioned 35 seismic stations wete given, and based on this,the outline of Moho surface was given.