On July 29, 2021, an earthquake with magnitude 8.2 occurred in the southern part of Alaska Peninsula, USA. In this study, the rupture process of this earthquake is inverted with far-field seismic waveform data for better understanding of the dynamic triggering. the results show that the slip distribution concentrated in adjacent area of the nuclear point, with 160km in length and 20km in depth. the slip model shows a rupture from deep to shallow indicating the stress energy in the shallow subduction zone released in this quake. the rupture process lasts for 120s, the maximum slip achieved 5m. In addition, the aftershock distribution lies in the south of mainshock which implies that rupture in the source region was developed well so as to trigger the earthquakes in the seaward of subduction zone. the distribution of aftershocks and slip displacement was limited in NE direction, not in the SW direction to Shumagin seismic gap, which infers the risk of large earthquake in the east of Shumagin area.