The circulation in the South China Sea (SCS) is mainly determined by the monsoons. This monsoon-induced circulation is connected with the circulation in the Pacific Ocean to a small extent and linked with that of the Indian Ocean only by the Timor Current. During winter, the water enters the South China Sea at the north through Formosa Strait and Luzon Strait, and exits at the south through Karimata Strait. During summer, the circulation reverses, the water enters at the south and exits at the north. Water from the north is generally cooler than water from the south. The northward (southward) flow induces warm (cold) advection. Therefore, the seasonal cycle of the circulation in the South China Sea becomes a major factor controlling the seasonal cycle of the sea surface temperature, which might effect the seasonal variation of the Eastern Asian monsoon system. In the preliminary results, the seasonal circulation and temperature patterns simulated by the primitive equation model are similar to those reported by Wyrtki(1961). Yet, our model is better than the Pohlmann (1987) shallow-water model and shows more details