In this thesis, I applied receiver function techniques to the data recorded by national and regional broadband seismic networks of the China Earthquake Administration to image the mantle transition-zone structure beneath eastern Asia. I analyzed a total of 37427 receiver-function data. Significant topography on both the 410-km and 660-km discontinuities was clearly imaged in the 3D volume of CCP stacked images that cover an area of 102.5°-122.5°E and 22.0°-42.°N. 3D crustal and mantle velocity models were used in computing the Ps time move-outs to better image the absolute depths of the two discontinuities. The 660-km discontinuity is depressed up to 25 km along the east coast of China, indicating the presence of the subducted Pacific slab in the region. A double 660-km was observed beneath the Yellow Sea. The 410-km is depressed by as much as 15 km beneath the Quaternary Datong volcano located at the northeastern edge of the Ordos plateau in north China.