The band inversion has led to rich physical effects in both topological insulators and topological semimetals. It has been found that the inverted band structure with the Mexican-hat dispersion could enhance the interband correlation leading to a strong intrinsic plasmon excitation. Its frequency ranges from several meV to tens of meV and can be effectively tuned by the external fields. The electron-hole asymmetric term splits the peak of the plasmon excitation into double peaks. The fate and properties of this plasmon excitation can also act as a probe to characterize the topological phases even in the lightly doped systems. We numerically demonstrate the impact of the band inversion on plasmon excitations in magnetically doped thin films of three-dimensional strong topological insulators, V-or Cr-doped (Bi,Sb)2Te3, which support the quantum anomalous Hall states. Our work thus sheds some new light on the potential applications of topological materials in plasmonics.Introduction.-Plasmons are ubiquitous collective density oscillations of an electron liquid and can occur in metals, doped semiconductors and semimetals [1,2]. The frequency of plasmon excitation is usually proportional to the density of states (DOS) of carriers at the Fermi level in the long wavelength limit [3]. In systems with vanishing DOS at the Fermi level, however, it had been demonstrated that strong correlation, higher order term in the effective mass, and the chiral anomaly could give rise to exotic plasmon excitations at zero temperature in the context of two dimensional (2D) Anderson insulators [4], graphene [5], HgTe quantum well [6], and threedimensional (3D) Weyl semimetals [7], respectively. In this paper, we reveal a new mechanism based on the band inversion with the Mexican-hat dispersion that can be used to excite and manipulate intrinsic plasmon excitations in topological materials even with vanishing DOS.