In this paper, from the viewpoint of meteorological observations and physics, a quantitative description method is defined to characterize the shear line strength in Yangtze-Huaihe River Basin, that is, an index(S_i), which can objectively and approximately describe shear strength near the shear line, is formed by synthesizing shear vorticity and divergence closely related to precipitation. On this basis, the relationship between shear strength and corresponding precipitation is analyzed, which shows that there is an obvious corresponding relationship between the strong shear strength area and precipitation and rain belt, and the precipitation area is usually consistent with the strong shear strength area or with a slightly southern displacement from it. Besides, a positive correlation between shear strength and precipitation intensity has been confirmed. When the index S_i=(∂u/∂y+∂v/∂y), the accumulated rainfall in the corresponding area for 6 hours exceeds 10 mm, even reaches 30 mm.