The Tibetan Plateau (TP) can exert profound influence on global and regional climate through its atmospheric heat sources (AHS). Previous studies have mainly focused on the impact of the AHS over the TP on climate anomalies in its downstream regions, while the regulatory role on adjacent Northwest China (NWC) has long been overlooked. This study investigates the relationship and physical mechanisms between summer AHS over the TP and precipitation variability in NWC on an interannual timescale. The results show that enhanced AHS over the TP increases precipitation in western NWC (WNWC) and decreases precipitation in eastern NWC (ENWC). Specifically, the enhanced AHS increases the meridional temperature gradient in Central and East Asia, causing an enhanced and southward westerly jet (WJ). This positions the WNWC/ENWC near the north of West/East Asia WJ exit/entrance, affected by positive/negative anomalous relative vorticity advection, favoring anomalous ascending/descending motion. Additionally, enhanced AHS strengthens the meridional circulations on both sides of the TP. The northern branch coupled with dynamic forcing of the WJ intensifies the anomalous descending motion in ENWC; while the southern branch suppresses precipitation in northern India and weakens its diabatic heating, inducing anomalous upper-level cyclonic and cold anomaly over Central Asia through thermal adaptation, which further modulates the WJ and moisture transport toward WNWC. Sensitivity experiments using the Linear Baroclinic Model also validate these findings. This study reveals the dynamic and thermodynamic mechanisms by which summer AHS over the TP regulates interannual precipitation variability in NWC, offering valuable insights for improving regional climate prediction and water resource management.