A new concept of thermodynamic shear advection parameter is introduced in this paper.Based on the parameter and the theory of wave-flow interaction,we conducted the diagnostic analysis on the heavy-rainfall event caused by landfall typhoon "Fung-wong".With the assimilation data of the ARPS mode,M and ▽·F were calculated to analyze the relationship between them and the observed 6 h accumulated surface rainfall.The result showed that the abnormal values of wave action density M(disturbance thermodynamic shear advection parameter) always covered the observed precipitation regions and both their horizontal distribution and their temporal evolution were quite similar.The positive high-value area of the parameter corresponded well with the observed 6 h accumulated surface rainfall.The analysis of ▽·F showed that in the process of rainfall which was caused by the landfall typhoon,the potential vorticity disturbance of ageostrophic wind was the main forcing term affecting the variation of disturbance thermodynamic shear advection parameter.Further analysis showed that the major exchange between the disturbance and basic states was the advection exchange of disturbance heat,while the advection exchange of disturbance momentum was very weak.