An MS5. 0 earthquake occurred in Jinkouhe in 2015. In order to reveal the internal relationship and dynamic background between the earthquake and the in- situ stress, the in- situ stress measurement data of hydraulic fracturing in two boreholes about 12km away from the epicenter were analyzed and studied, the stability of faults in the northern Ebian- Jinyang fault zone is analyzed by using by Byeerly’s criterion and stress Mohr’s circle, and the dynamic background of the occurrence of the Jinkouhe earthquake is discussed in combination with the value of seismicity parameter b. The results show that, within the depth of 94.90 to 722.10 meters, the maximum horizontal principal stress is 5.89 MPa to14.50 MPa, and the minimum horizontal principal stress is 3.79 to 10.30 MPa; that the maximum horizontal principal stress direction is N50° W to N68° W, which tends to be Northwest to West direction, consistent with the regional tectonic stress field; that the relative magnitude of the triaxial principal stress of YJP- 1 borehole is favorable for the activities of reverse fault and strike- slip fault, while the relative magnitude of the triaxial principal stress of DPS- 1 borehole is favorable for the activities of normal fault; that the average value of μm (ratio of maximum shear stress to average stress) under the effective stress condition of DPS- 1 borehole is 0.46, which is close to the lower limit of fault friction sliding threshold of 0.51, and is favorable for normal fault sliding, and that the stress locking concentrated area in the bending structure of Emei- Yanfeng fault is the main reason for the weak horizontal structure near the borehole. The research results are of great significance for revealing the dynamic background before the Jinkouhe MS 5. 0 earthquake.