Topological insulators (TI) represent a new state of quantum matter with a bulk gap and odd number of relativistic Dirac carriers on the flat surface. The mechanism for the topological insulating behavior in these 3D materials is the band inversion of the conduction and valence edge states caused by large spin-orbit coupling (SOC). Taking into account that new physics and phenomena related to topological state of the matter emerged search of new topological materials have been emerged last years, inclusive among the multinary ternary compounds. The first family of ternary of TIs identified recently [1] dealing with rhombohedral thallium-based III-V-VI2 ternary chalcogenides. This ternary semiconductors are structurally and electronically related to the binary narrow gap IV-VI compounds. Its crystal structure can be viewed as the distorted NaCl structure with four atoms in the primitive unitcell. Taking TlBiTe2 as an example we can observe atoms are placed in layers normal to the three-fold axis with the sequence -Tl-Te-Bi-Te-.Such layered structure is similar to thermoelectrics semiconductors Bi2Te3, Bi2Se3, and Sb2Te3, which were the first binary compounds identified to be TI. For Bi2Se3, five atomic layers form a quintuple layer and the coupling between two quintuple layers is very weak and materials are layered. In TlBiTe2 electron shells for Tl, Bi and Te are all p-orbitals (6p1 for Tl, 6p3 for Bi and 5p4 for Te) and each Tl (Bi) layer is sandwiched by two Te layers, therefore there is strong coupling between every two atomic layers for TlBiTe2 and the crystal structure is essentially 3D. Starting from p-character of the bonds, proximity of the crystal structure to cubic one and concept of Pierls instabilty 20 years ago a theory of electronic structure rhombohedral thalliumbased III-V-VI2 ternary compounds was developed [2]. For IV-VI semiconductors in the FCC lattice, the top of the valence bands is located at the L-points. In the thalium based ternary compounds due to cationic ordering and trigonal displacement the unit cell is doubled along a particular (111) axis. In the results the top of the valence bands at one L-point is folded to the G-point, and those at the other three L-points are folded to three equivalent X points. On this basis several thallium-based semiconductors was shown to have band inverted spectra at G and L points in the Brillouin zone due to strong SOC and therefore it is not surprisingly to find its at present among TI. For deeper understanding and quantitative predictions of novel phenomena associated with the TIs, it is highly desirable to construct standard models for both 2D and 3D TIs. In this paper, on the basis of developed early theory [2] we give the microscopic derivation of model Hamiltonian for topological states of rhombohedral thallium-based III-V-VI2 ternary compounds, first by constraining its form by symmetry principles, a careful analysis of the relevant atomic orbitals and kp perturbation theory. On this basis the following Hamiltonian is obtained for four band edge topological states with the spin degeneracy at G point offormulasx,y,z are the Pauli matrices, P1+ denotes the conduction band and P2- - the valence, symbols indicate the state of the spin. Combining the k p perturbation scheme with the theory calculation [2], we can numerically calculate the parameters of the model have been established. The positive values of the parameters M , B1 and B for TlBiTe2 indicate that the system stays in the G band inverted regime and is topologically nontrivial. Thus this band topology will generate metallic surface states which are the hallmark of topological insulators. For the [111] surface in III-V-VI2 ternary there are four possible surface terminations and the topologically protected surface states may coexist with non-topological ones arising from dangling bonds, leading to a complicated surface spectrum.