Abstract The Tangra Yumco Rift (TYR) in central Tibet is a key window for crust–mantle interactions during extension. We performed high‐resolution crust‐mantle imaging using receiver function analysis, 1‐D nonlinear S‐wave velocity inversion, and tomoDD tomography, revealing a vertical Crust–Mantle Degassing System (CMDS) bounded by the Zhala (ZF) and Wozang (WF) Faults. Two mantle low‐velocity zones (MLVZ1/2) at ∼70 km are interpreted as Neo‐Tethys and Shiquanhe–Jiali Tethys Ocean remnants, respectively. Crustal low‐velocity zones (20–40 km, Vs < 3.5 km/s) correlate with high‐conductivity bodies, serving as fluid migration pathways. Mantle‐derived CO2/3He, generated by partial melting of carbonate‐rich oceanic remnants, migrate upward via crustal conduits formed by brittle‐ductile decoupled deformation. This study links deep lithospheric dynamics to surface degassing and ecological anomalies, providing a new paradigm for lithosphere–biosphere feedback within plateau rifts.