Using subsurface buoy data during November 2010 to July 2011, the south flow, which is under the northward Kuroshio Current between 400 m to 700 m, was studied. According to the time series available from subsurface buoy, the seasonality of the south flow strength is winter > summer > spring. In addition to the Acoustic Doppler Current Profiler (ADCP) data, satellite altimeter data, the SODA 2.2.4 and the World Ocean Database 2009 (WOD09) were further analyzed and a possible influence mechanism is: the intraseasonal variation (winter>summer>spring) of the south flow is mostly influenced by mesoscale eddies east of Luzon, indicating that the observed flow is a combination of background flow and eddy-induced flow. With the consideration of oscillating of the source of the Kuroshio which affected the on observation, we calculated the axis of the source of the Kuroshio based on HYCOM data by using weighted average method. A number of features of the Kuroshio axis were identified. During November 2010 to July 2011, significant intraseasonal variability of the distance between Kuroshio axis and the longitude of buoy (122.7°E) was exposed. The whole layer had influence on the axis from surface to 700 m. Therefore, another possible influence mechanism is: The observed flow is also influenced by the horizontal oscillation of the Kuroshio axis, the observed meridional velocity is higher when the distance is smaller, and vice versa.