Using the CAP method to invert the focal-mechanism solution of the Xinyuan-Hejing MS6． 6 earthquake on June 30，2012． The result shows that the best double couple solution of the MS6． 6 event is 299°，68° and 164° for strike，dip and rake angles respectively． The other nodal planes are 35°，75° and 23°． The azimuth and dip angle of P axis are 166° and 5°，those of T axis are 258° and 26°． The moment magnitude is 6． 3． The estimated focal depth is about 21km． The predominant rupture direction of this seismic sequence is NWW． The dip angles are between 60° and 90°． The rake angles are basically ± 180° ± 30°． The predominant strike of the azimuthal angle of P axis is near NS and T axis is near EW． Preliminary analysis indicates that nodal section． One is the seismogenic fault and NWW-trend and nearly upright left-lateral strikeslip fault． The displacement property and the principal compressive stress of this MS6． 6 earthquake focus and P axis preponderant orientation of this seismic sequence agree with the tectonic stress field＇s characteristics of the focal area around．