Considering multiple dynamic factors of the river discharge, tide and tidal current, topography, mixing and continental shelf current, a modified 3-D numerical ECOM model was used to study the impact of wind stress and Coriolis Force on the formation of a freshwater zone in the Meimaosha area in the South Passage of the Changjiang Estuary. There existed freshwater zone in Meimaosha area during dry season, and its formation dynamic mechanism is mainly the Changjiang runoff and tidal current oscillation. The numerical calculation results in this paper indicate that onshore Ekman transport induced by the north wind during dry season result in a wind-driven circulation, which flows toward land in the North Channel and flows toward sea in the South Channel in the bifurcation estuary. This wind-driven current prevents the saltwater intrusion from the out sea, and consequently, facilitates the formation of the freshwater zone in the South Passage. The Coriolis Force turns the water flow to the right in the northern hemisphere, and drives the upstream freshwater move downstream along the Nanhui tidal flat, which facilitates the formation of the freshwater zone in the Meimaosha area.