The LASG/IAP climate system ocean model (LICOM), a quasi-global 1/10° eddy-resolving ocean general circulation model, was used to simulate the seasonal variation of water exchange in the Luzon Strait. The seasonal variation in the upper circulation and the Luzon Strait Transport (LST) were found to be significant. Except for the eastward LST in June, westward LST dominates all other months. The biggest LST occurs in winter. The mean LST is estimated to be approximately -3.76 Sv (1 Sv=106
/s), and the upper-layer (600 m) flux is the major contributor (-3.60 Sv). The South China Sea (SCS) exchanges waters with its adjacent oceans through six straits. The Luzon Strait and the Balabac Strait are the main channels through which the ocean water flows into the SCS. The Taiwan Strait (1.99 Sv) and the Karimata Strait (1.03 Sv) take the first and second places of the four outflow straits. A mechanism analysis shows that Ekman transport caused by monsoon events accounts for only 11% of the LST. However, the westward geostrophic current, resulting from a pressure gradient caused by monsoon events, plays a dominant role in the water exchange of the Luzon Strait. As the source of the Kuroshio, the North Equatorial Current also has some impact on the seasonal variation of the LST.