Abstract:The focal mechanism solutions of 68 small and medium earthquakes, whichoccurred in the southeastern margin region of Taihang mountains fault zone (TMFZ) ,are determined by the amplitude ratio of PG and SG in vertical component records with clear initial motion. The parameters of focal mechanism solutions are analyzed using statistical and cluster analysis.The average stress field azimuth of area is calculated with the method of mechanical axis tensor. The results show that the main focal mechanism solutions arestrike-slip type in the research area, and the proportion is 57%. There are also normal and inverse fault types. The dips of both maximum and minimum stress axis are small, relatively close to level. The analysis indicates that the main characteristics of the tectonic stress field of research area are nearly NEE-SWW compression and nearly NNW-SSE expansion.