In multilayer integrated circuit, the parasitic mode problem is caused by Defect Ground Structure(DGS). By comparing the effects of window shielding form and various back hole arrays in suppressing the propagation of parasitic modes, it is found that the window shielding form can effectively suppress the propagation of parasitic modes but greatly increase the circuit loss. The existence of the simplest back hole array can achieve parasitic suppression. Without changing the process structure, the double-back-hole form and the four-back-hole form can meet the suppression requirements of dielectric films below 200 GHz and 300 GHz respectively. In these cases, the back holes occupy the smallest area. It can effectively reduce the back hole arrangement density and increase the circuit integration.