On the basis of previous studies, a thermodynamic shear advection parameter is defined by involving vertical component and horizontal divergence of convective vorticity vector, and vertical gradient of generalized potential temperature. The parameter is characterized by describing dynamical characteristics of horizontal wind shear and thermodynamic characteristics of downward funnel-shaped moist isentropic surface over extreme weather regions. The parameter is calculated with NCEP/NCAR global final analysis data in two heavy-rainfall events in China. The result shows that the positive high-value area of the parameter vertically integrated always covered the observed 6-h accumulated surface rainfall. Both of them shared a similar horizontal distribution pattern and an analogous temporal evolution trend. The parameter in the precipitation zone showed a strong signal, while it presented a weak signal in the non-rainfall areas. Since the parameter is capable of presenting typical vertical structure of dynamical and thermodynamic fields over extreme weather area, it is closely related to the precipitation weather system leading to heavy rainfall. This is the reason that there is a corresponding relationship between the parameter and the observed 6-hour accumulative rainfall areas. It was also shown that the precipitation area was covered by the abnormal-value region of flux divergence term in the parameter equation. This indicated that the flux divergence prompted the parameter to revolve over the precipitation area. The contribution to the local change of the parameter from the interaction between zonal and meridional winds in the flux divergence term is chief.