Abstract: The subduction of the Pacific Plate towards the North American Plate has formed a collisional mountain belt and subduction zone at the edge of the continent in Alaska. Previous studies on the mantle transition zone beneath the Alaska subduction were in debate. It is believed that the thickening of the transition zone is due to the subduction of the Pacific Plate, or due to the thickening is caused by the residual Kula Plate. Therefore, accurate imaging of mantle transition zones in the Alaskan subduction zone is of great significance for understanding the subduction mechanism and courses of the Pacific Plate. This study provided waveform data from teleseismic events received in several stations of the US Array deployed by Incorporated Research Institutions for Seismology (IRIS) in the Alaska region, and adopts the natural earthquake P-wave receiver function and common conversion point stacking method to obtain 410 km and 660 km discontinuity sections and mantle transition zone thickness structure of the Alaska Range and Yukon Plateau. The new results show that due to the subduction of the Pacific Plate into the mantle transition zone, a 410 km long discontinuity is uplifted in the arc-shaped area of the eastern Alaska Mountains and the junction of the Yukon Plateau and the Alaska Mountains, with an uplift of 0～20 km, which in turn led to different degrees of thickening of the mantle transition zone in this area, which verifies the first view. In addition, the structure of the mantle transition zone in this area shows that a 660 km long discontinuity has subsided in the eastern part of the Alaska Mountain Range and the eastern part of the border between the Alaska Mountains and the Yukon Plateau. Therefore, it is assumed that the Pacific Plate in parts of south-central Alaska has subducted to the bottom of the mantle transition zone.