In this paper, the WRF model and LAGRANTO trajectory model are used to carry out numerical simulation and trajectory analysis of typhoon Malakas (2010) during its extratropical transition, analyzing the impact of typhoon Malakas on the midlatitude flow and the structural change characteristics of Malakas during the interaction process. The analysis shows that Malakas has experienced three stages during its extratropical transition:(1) During the upper disturbance intensifying, the cyclonic circulation generated by high-level positive Potential Vorticity (PV) generates negative temperature advection on the west side of the baroclinic zone in the northern part of the Malakas center, which is manifested as the invasion of cold air. (2) During the TC-midlatitude flow interaction period, the typhoon heads northward and leads to the occurrence of the baroclinic zone. The deep convection eruption causes the low-level warm wet air to rise along the baroclinic zone, and the release of latent heat in rapidly ascending air leads to a net transport of low-PV air into the upper troposphere to rebuild a ridge in the part of north. (3) During the extratropical cyclone stage, the remnants of the TC inner core merges with the baroclinic zone. The negative PV advection by the diabatic driven outflow initiates ridge building, accelerates and anchors a midlatitude jet streak, and overall amplifies the upper-level Rossby wave pattern.