On March 22, 2025, an M_S3.3 earthquake struck Liuhe County, Tonghua City, Jilin Province. To better understand the source characteristics, seismogenic structure, and present-day tectonic activity of this event, we conducted comprehensive analyses incorporating moment tensor inversion, source parameter inversion, fault instability evaluation, and regional stress field assessment. Additionally, regional depth phase (sPg) observations were used to further constrain the focal depth. The focal mechanism solution indicates that nodal plane Ⅰ has a strike of 232°, dip of 88°, and rake of -172°, while nodal plane Ⅱ has a strike of 141°, dip of 88°, and rake of -2°. Nodal plane Ⅰ aligns with the southwest-trending Sanyuankou-Yangzishao fault near the epicenter, suggesting that this fault is likely the seismogenic structure. The rupture exhibits a typical right-lateral strike-slip motion with a minor extensional component. This faulting style contrasts with the compressive nature previously assigned to the Sanyuankou-Yangzishao fault in the Regional Geology of Jilin Province. Moment tensor inversion and depth phase analysis constrain the focal depth to approximately 8km—significantly shallower than the 15km reported by the China Earthquake Networks Center(CENC). The derived source parameters include a static stress drop of 6.4MPa and an apparent stress of 1.4MPa, both within the typical range for small earthquakes in continental China but slightly above their respective median values, implying relatively high stress accumulation in the source region. These findings enhance the understanding of the current activity of regional faults and provide a scientific basis for seismic hazard assessment and integrated disaster mitigation planning in the Liuhe area.