The invention belongs to the technical field of satellite communication antennas, and particularly relates to a method for designing a slow wave structure of a CTS antenna and a VICTS antenna. Firstly, a parallel plate waveguide dispersion equation model based on a uniform rectangular comb tooth slow wave structure is established to establish a parallel-plate waveguide dispersion equation model with a uniform rectangular comb tooth structure based on horizontal radiation branching; according to the two dispersion equation models, obtaining a mapping relationship between an effective dielectricconstant of a horizontal radiation branching unit and rectangular comb tooth structure parameters and the height of a parallel plate waveguide; finally according to the VICTS antenna design requirements, choosing a variation rule, function or curve of the height of the parallel plate waveguide, and according to the obtained mapping relationship, selecting the corresponding rectangular comb toothstructure parameters under different parallel plate waveguide heights. According to the method for designing the slow wave structure of the CTS antenna and the VICTS antenna, by the nonlinear design on rectangular comb teeth which are of the slow wave structure in the VICTS antenna, while array optimization is achieved, it is ensured that parameters such as the gain of the antenna and the standing-wave ratio do not deteriorate or even are improved.