Abstract: For infinite long North-South valleys, the present thesis has developted a two-dimensional nonhydrostatic model, which includes topography. It has been studied in detail how the wind speeds and directions in the valley depend on the cross-angle between the airflow directions and the valley axis, the valley width, the valley deep, the valley relative deep and the temperature stratification. The simulated results agree quite well with the real observed statistical results made at Sanxia Valley.