The mean velocity structure and variability of the Kuroshio east of Taiwan, China, were investigated using mooring observations acquired at 23°N/122°E between January 2016 and May 2017. Power spectrum analysis reveals marked intraseasonal variability in 70–95 days in the meridional Kuroshio velocity in the upper 800 m. Hybrid Coordinate Ocean Model assimilation data adequately reproduce variations of the Kuroshio. Westward propagating mesoscale eddies that originated from the Subtropical Countercurrent play an important role in intraseasonal variability in the Kuroshio velocity. Cyclonic (anticyclonic) eddies are often associated with negative (positive) sea surface height anomaly, resulting in positive (negative) potential vorticity in the subsurface layer of the eddy center, which decreases (increases) isopycnal slope and then weakens (strengthens) the Kuroshio. When anticyclonic (cyclonic) eddies are active, the Kuroshio axis moves offshore (inshore). Corresponding to the Kuroshio intraseasonal variability (ISV), the variation of the intermediate water salinity also had a significant ISV induced by the mesoscale eddies.