Abstract: Based on MPV equation and the theory of slantwise vorticity development,the possible relationship between the abrupt intensity change of tropicalcy clone and the evolution of its equivalent potential temperature structure is studied in this paper.A set of high resolution model out put data is used to verify the result.Analyses show that,because the moist isentropic surfaces are extremely steep in the eyewall region,the change of moist baroclinity is a main cause for abrupt change of vertical vorticity there.If the vertical vorticity increases rapidly in most regions,the tropicalcy clone will experience explosive deepening.Some discussions on how the concentric eyewall structure affects the intensity of tropical cyclone are also proposed.