Abstract: Based on satellite data from 1993 to April 2025, this study employs the Sobel operator and Canny edge detection algorithm to extract the West Subarctic Front (WSAF) in the Northwest Pacific. The frontal characteristics of the WSAF are analyzed, and the impact of the northward acceleration of the Kuroshio Extension (KE) on the KE-WSAF system and the hydrological evolution of the Kuroshio and Oyashio Confluence (KOC) during the Kuroshio large meander period from August 2017 to April 2025. The results show that since 1993, the KE has experienced a long-term northward migration rate of (0.53±0.09) (°)/(10 a), while the WSAF has also shown a northward trend with a long-term migration rate of (0.19±0.08) (°)/(10 a). The difference in northward migration rates between the KE and WSAF has led to a sustained contraction in the meridional extent of the KOC, with a contraction rate of (−0.30±0.09) (°)/(10 a). During this large meander period, the northward migration rates of the KE and WSAF (1.31±0.56) (°)/(10 a) and (0.72±0.63) (°)/(10 a), respectively increased to 2.5 times and 3.8 times their long-term rates, respectively. The intensity of the WSAF frontal zone exhibits spatial variability, with strengthening in the northern section and weakening in the southern section. The area of the WSAF has significantly diminished, reversing the slow long-term trend of area expansion. Sea surface temperatures in the KOC have reached their highest levels since 1993 (with positive anomalies up to 3.18 ℃), accompanied by enhanced salinity oscillations. Concurrently, turbulent heat fluxes from the ocean to the atmosphere have generally increased in the region north of the KE. Corresponding to the sea surface temperature dipole anomaly in the southern WSAF, a pronounced dipole pattern of turbulent heat flux anomalies has emerged between the eastern and western areas. This study elucidates the long-term trends of the WSAF and the response of its frontal characteristics, along with the surface hydrological properties of the KOC, to KE dynamic changes during the recent Kuroshio large meander period, providing a reference for further investigation into the role of such oceanic events in regional oceanography and climate.