This study utilized ERA5 reanalysis data and multiple observations to investigate the weakening and strengthening of the remnant vortex of Typhoon Doksuri (2023) in the Northwest Pacific after its landfall. It caused significant damages in northern China. The main maintenance and recovery period were observed from the night of July 29th to the daytime of July 30th. The study result reveals that during the maintenance of the remnant vortex, it had a warm-core structure and was not influenced by dry and cold air. During the recovery process, a noticeable increase in water vapor convergence and moist potential vorticity were observed on the northeastern side of the remnant vortex center. Additionally, the northward movement of the remnant vortex was hindered by a zonal subtropical high belt, causing a reduction in its northward-moving speed. Under the guidance of a mid- and high-level high-pressure system, the dry and cold air further intensified the temperature and moisture gradients between the mid- and low-level remnant vortex and warm-moist air masses, resulting in a clear tilt of isentropic surfaces on the northern side of the vortex. This tilt in isentropic surfaces led to the vertical development of cyclonic vortex. Furthermore, during the maintenance and recovery period, the remnant vortex continued to receive some heating from the increased soil moisture. Additionally, significant condensation latent heat was released due to radial moisture inflow and vertical upward motion on the northeastern side of the remnant vortex. This release of latent heat provided necessary conditions for the maintenance and strengthening of the remnant vortex.