Using the system cluster of focus mechanism solutions for moderate-strong earthquakes and the stress field inversion of focal region in the Jiashi strong earthquake swarm from 1997 to 1998, main result as followed are obtained：（1） The Jiashi strong earthquake swarm is characterized mainly by strike-slip and normal fault. The axis of principle compressive stress is oriented mainly to NNE or nearly NS, which is inconsistent with the regional tectonic stress field of the adjacent Kalpin block. The rupture plane of the Jiashi strong earthquake swarm is oriented NEE, belong to left-lateral rupture. （2） From the stress field inversion of moderate-strong earthquakes with M4-5, we obtains that the maximum compressive stress axis is NNE, the minimum one is NWW, the＇dip angle of medium stress axis is 65°, which is upright. （3） The stress field in the focal region had a change process before and after those strong earthquakes. Finally, certain discussion to the result is given.