A numerical model is developed to explain the response of the shelf sea to the abrupt imposition of a steady, secular mean windstream field and the basic characteristics of the wintertime circulation in the Northern Huanghai Sea (Yellow Sea) and the Bohai Sea by using equidistant, staggered grid points, an implicit finite difference scheme and our new “splitting computational method” of adjustment, development, and dissipation processes. So far as the major tendency of the circulation is concerned, the numerical result agrees with the observational data. The computational results show that the eastern anticyclonic and the western cyclonic circulations constitute the main body of the wintertime circulation in the Northern Huanghai Sea, and that the northern anticyclonic and the southern cyclonic circulations constitute the main body of the wintertime circulation in the Bohai Sea. A numerical model is developed to explain the response of the shelf sea to the abrupt imposition of a steady, secular mean windstream field and the basic characteristics of the wintertime circulation in the Northern Huanghai Sea (Yellow Sea) and the Bohai Sea by using equidistant, staggered grid points, an implicit finite difference scheme and our new “splitting computational method ” of adjustment, development, and dissipation processes. the far more than the major tendency of the circulation is, the numerical result agrees with the observational data. computational results show that the eastern anticyclonic and the western cyclonic circulations constitute the main body of the wintertime circulars in the Northern Huanghai Sea, and that the northern anticyclonic and the southern cyclonic circulations constitute the main body of the wintertime circulars in the Bohai Sea.