The winter counter-wind current (also named the South China Sea Warm Current (SCSWC)) in the northern South China Sea (SCS) has been known well for decades, but its mass and momentum origination have not be quantitatively evaluated before. In this paper, the high resolution three-dimensional ocean circulation model is adopted to reproduce the circulation in the northern SCS. The diagnostic analyses are performed to investigate the momentum budget in the northern SCS continental shelf/slope and the momentum propulsion of the SCSWC. It is indicated that the across-shelf pressure gradient and the across-shelf transport are responsible for the formation of the SCSWC, while the along-shelf pressure gradient is balanced by the surface stress, bottom stress, and Coriolis force. The magnitude of the terms in the along-shelf momentum equation is smaller than that in the across-shelf one. The analysis on the momentum budget in the northern SCS will benefit the marine environmental prediction in the future. The winter counter-wind current (also named the South China Sea Warm Current (SCSWC)) in the northern South China Sea (SCS) has been well well for decades, but its mass and momentum origination have not be quantitatively evaluated as before. paper, the high resolution three-dimensional ocean circulation model is adopted to reproduce the circulation SCCWC. The diagnostic analyzes are performed to investigate the momentum forecasts in the northern SCS continental shelf / slope and the momentum propulsion of the SCSWC. It is indicated that the across-shelf pressure gradient and the across-shelf transport are responsible for the formation of the SCSWC, while the along-shelf pressure gradient is balanced by the surface stress, bottom stress, and Coriolis force. The magnitude of the terms in the along-shelf momentum equation is smaller than that in the across-shelf one. The analysis on the momentum budget in the northern SCS will benefit the marine environmental prediction in the future