Abstract: Based on the theory of multimode coupling, the electromagnetic characteristics of the millimeter wave Bragg structure with double inner conductors and three inner conductors are compared by using the 3D electromagnetic simulation software CST. The results show that the double inner conductor Bragg structure can suppress the competitive mode compared with the coaxial Bragg structure, the reflectivity is stable and close to 1, and the electromagnetic characteristics of the symmetric structure is better than the asymmetric structure; With the increase of the distance between the inner conductor and the coaxial axis, the bandwidth of the double inner conductor Bragg structure frequency response becomes wider, and when the inner conductor is far from the coaxial axis, the bandwidth becomes wider obviously, while the value of reflectivity tends to be stable; For the three inner conductor Bragg structure, the frequency response bandwidth narrows with the increase of the distance between the inner conductor and the coaxial axis, and the bandwidth widens obviously when the inner conductor is close to the coaxial axis. Therefore, the Bragg structure parameters of millimeter wave inner conductor can be properly selected according to the actual needs to broaden its performance as a reflector or filter, improve the selectivity and purity of the mode, and improve the performance of the Bragg structure.