We used global seismic tomography and regional tomography to study the deep structure and origin of the Changbai intraplate volcano in Northeast China. Our results reveal a lowvelocity anomaly extending to 400 km with a velocity reduction of up to 4%. High velocity anomalies are visible in the mantle transition zone, and deepfocus earthquakes occur at depths down to 600 km under the region,suggesting that the subducting Pacific slab is stagnant in the mantle transition zone under Northeast Asia.These results suggest that the intraplate Changbai volcano is not a hotspot like Hawaii but a kind of backarc volcano related to the deep subduction and stagnancy of the Pacific slab under Northeast Aisa.