The circulation of the Japan/East Sea (hereafter JES) is a central problem of physical oceanography. Uda (1934) gave the first schematic surface current chart for this area. Moriyasu (1972) summarized the general hydrographic features of the JES. Yoon (1982 a-c) and Kawabe (1982 a,b) pioneered research on the JES circulation was focused on the path of the Tsushima Current. After then, many numerical simulations of the JES circulation were reported. The formation of the East Korean Warm current (EKWC) is one of the most important problem in the JES circulation Some early investigators (Yon, 1982a; Kawabe, 1982b; Kang, 1988; etc.) suggested that the EKWC is a western boundary current induced the planetary β-effect. Their results showed the EKWC is a permanent current. It is very strange that the EKWC did not appear at all in 1981 (Kim and Legeckis,1986). So it is necessary to study further the driving force of the EKWC. In this study, a Princeton Ocean Model (known as POM97) was employed to simulate the circulation in the JES. The open boundary inflow and outflow conditions with realistic water depth in the numerical model are first set. Then, several experiments with artificial topography were made to test how the topography affects the circulation pattern in the JES.