In this paper, a metamaterial structure based on a periodic square-ring array of three-dimensional topological insulators Bi1.5Sb0.5Te1.8Se1.2 is proposed. The simulation results show that the surface plasmon resonance intensity of the metamaterial structure is enhanced with increasing the array period and the size of square ring, where 80% of the electromagnetic wave can be confined to the surface states when the period is 300 nm or the size is 25 nm. In addition, the circular dichroism of the metamaterial and non-metamaterial structures under positive and oblique circularly polarized light incidence are obtained by simulating the relationship between the variation of the surface electric field with the polarization of the metamaterial and non-metamaterial structures under positive and oblique incidence. The circular dichroism of the metamaterial structure of 0.92 is much larger than that of the non-metamaterial structure, and there is a significant increase in the ratio of the circularly polarized component to the total polarized component for this metamaterial structure, which is attributed to the fact that more spintronic electrons are excited by the circularly polarized light from the topological surface state to the body conduction band.