The traditional plate tectonic theory has limitations in explaining continental earthquakes, and the thermal structure of the lithosphere serves as a crucial window for exploring the mechanism of intraplate earthquakes. Based on geothermal data from Ningjin and its adjacent areas in North China, combined with the crustal layered structure revealed by deep seismic sounding profiles, this study employs a 2D finite element method to numerically simulate the deep temperature field of the study area, characterize the features of the lithospheric thermal-rheological structure, and explore its relationship with seismic activity. The results indicate that from the Taihangshan Uplift to the Linqing Depression, the mantle heat flow exhibits a low-to-high trend, the "thermal" lithospheric thickness shows a thick-to-thin variation, and the Moho temperature displays a high-to-low-to-high pattern. The crust-mantle heat flow ratios in the eastern Jizhong Depression and Linqing Depression range from 0.66 to 0.72, indicating intense deep-seated activities. Seismic events in the study area are spatially concentrated in terrestrial heat flow gradient zones, local Moho uplift zones, and areas with well-developed deep and large faults. Vertically, they display a two-layer distribution, with the boundary defined by the Brittle-Ductile Transition Depth (BDTD) in the middle crust. Lateral variation zones of the thermal structure are concentration areas of thermal stress; BDTD demarcates the two-layer distribution of earthquakes; and deep and large faults controlled by the thermal structure serve as the key carriers for the upwelling of mantle thermal materials and stress transfer. Under the influence of the subduction of the Pacific Plate, mantle upwelling triggers back-arc extension, which results in lithospheric fragmentation and disturbs the intracrustal temperature and stress fields. The coupling of thermal stress and tectonic stress further forms the two-layer seismic fracture pattern.