Abstract: For the problems of high-precision processing requirements from complex elements′ structure in the topology optimization of metamaterial microstrip antenna, this paper proposes a minimalist design concept: the Bagua element; and the topology optimization design of the metamaterial microstrip antenna is completed based on the Bagua elements, which not only ensures the high gain performance of the antenna, but also has a simple metamaterial structure and good manufacturability. The metamaterial structure is composed of invariable arc elements and changed Bagua elements, and each Bagua line in Bagua elements corresponds to one design variable, which value rules are as follows: 1 corresponds to the continuous Bagua line, and 0 corresponds to the broken Bagua line. Then taking maximization of the antenna gain as the design objective, setting the working frequency of 24 GHz as constraint, a topology optimization model for the design of metamaterial microstrip antennas is established; and based on the solution strategy of genetic algorithm, the symmetric and asymmetric metamaterial microstrip antennas are studied respectively. The results show that the gain of metamaterial microstrip antennas based on Bagua elements can be significantly improved, moreover the metamaterial antenna of Bagua element with four lines has greater gain; and the symmetry of the metamaterial structure can ensure that the Z axis is the main direction of radiation direction; the sample results verify the good preparation of the Bagua element metamaterial microstrip antenna; from the in-depth analysis of topology optimization design it is found that the Bagua element design is more efficient, compared with the square lattice element. Finally, the mechanism of high-gain metamaterial microstrip antennas is explained from the perspective of the surface wave.