Abstract: In 1951—1952 some earthquakes occurred in the studied area. Preliminary investigation shows that the Bengcuo earthquake deformation belt is well developed, in which deformation structural types are various. The most strong deformation occurred near Dagza southeast of Bengcuo, of which the location coincides basically with that of the main shock epicentre. The belt is straight, trending N310°W, about 100km long and several to 20m wide or more and characteristic of a dextral strike-slip with the greatest offset of about 12m. The NW-trending one is dextral, dominated by strike-slip displacement and having dip-slip faults which are mostly obscure. And the NE-trending one is sinistral, dominated by dip-slip displacement and having strike-slip faults with small displacement. The nearly NS-trending one is characteristic of a tensile normal fault. The above mentioned belts also basically extend along the boundary fractures or secondary fractures. Naturally, the NW/NE-trending belts should be considered as a set of conjugate fractures.Viewed from the directions of the large-scale deformation belts associated with some aftershocks, strictly controlled by the boundary fractures of the active tectonic zones. It is most likely that the aftershocks in the studied area are of tectonic shocks responding to successive releasing of ground stresses following the main shock, although no data on focal depth are available at present.In summary, earthquake-controlling structures in the seismic area should be the active tectonic zone (No.2) of an active tectonic system in Southern Tibet, controlling stress concentration and migration in the seismic area. The earthquake-generating structures should be on NW/NS-trending boundary fractures and at their intersection of active tectonic zones, where are favorable to the regional stress release.Analysis of the earthquake-controlling structures and seismostructures indicates that their stress fields show more or less consistent characteristics, which are similar to that in the Tibet plateau, the orientation of maximum principal compression stress trending NS and the maximum tension, approximately EW.