This paper proposes a metamaterial structure based on a periodic square-ring array of three-dimensional topological insulators (Bi_1.5Sb_0.5Te_1.8Se_1.2). Simulation results showed that the surface plasmon resonance intensity of the metamaterial structure was enhanced with decreases in the array period and size of the square ring, where 80% of the electromagnetic wave could be confined to the surface states when the period was 300 nm or the size was 25 nm. In addition, the circular dichroism of the metamaterial and non-metamaterial structures under the incidence of positive and oblique circularly polarized light were obtained by simulating the relationship between the variation of the surface electric field and polarization of the metamaterial and non-metamaterial structures under positive and oblique incidence. The circular dichroism of the metamaterial structure (0.92) was much larger than that of the non-metamaterial structure, and there was a significant increase in the ratio of the circularly polarized component to the total polarized component for this metamaterial structure, which was attributed to the fact that more spintronic electrons were excited by the circularly polarized light from the topological surface state to the body conduction band.