Abstract: Under single-well observation, the micro-seismic event location is usually using the time difference between P- and S-wave, and adjusted P-wave to calculate the distance and azimuth between the event and geophone, respectively. The real hydraulic fracturing monitoring data often contains lots of single S-wave micro-seismic events, but S-wave generally cannot be used for the calculation of azimuth, which brings difficulties for the location of single S-wave events. However, the focal mechanism inversion study indicates that the focal mechanism of micro-seismic events is closely related to the location, which provides the possibility of single S-wave events location under single-well observation. For the single S-wave events difficult location problem in real hydraulic fracturing data under single-well observation, based on ray tracing location and single-well focal mechanism inversion technology, this paper proposed a solution method by comparing the strike angle of focal mechanism between all feasible location and its nearest double phase micro-seismic event, whether meet similar or orthogonal as the constrain condition. Synthetic data test indicates that although this method localization error of the single S-wave event is greater than the double phase event, it is still within the acceptable range and is feasible. The real data application works well. The spatial distribution of micro-seismic events is consistent with the regional tectonic stress direction. The focal mechanism of events indicates that the rock fracture surface is mainly along the maximum or minimum horizontal stress direction, and the fractures are mostly high angles. This paper provides a feasible idea for single S-wave micro-seismic events location in single-well observation.