Flowing along the Luzon Strait and east of Taiwan Island, the Kuroshio Subsurface Saline Water (KSSW) in the source region can carry large amounts of energy, heat, salt and climate change signal from the Pacific to the South China Sea and East China Sea. So, it has a large impact on the circulation pattern, hydrographic condition, ecological environment and climate change in China Seas. At present, however, there are fewer studies on the KSSW in the source region. Therefore, the spatial and temporal variation of KSSW, and its dynamic mechanism remain unclear, and need to be further studied. Thus, based on the analysis of historical data, theoretical analysis and numerical simulation, we try to investigate the spatial and temporal variation of KSSW in the source region, and study the effects of Kuroshio transport, wind, North Equatorial Current, mesoscale eddies and ENSO on the spatial and temporal variation of KSSW, and clarify its dynamic mechanism. This study can improve our understanding and predicting on the influence process of Kuroshio in the source region on the ecosystem in China Seas from a new point of view, and provide scientific basis and technological support for the protection of ecological environment and fishery resources.