The dispersion equation of the coaxial interlaced disk-loaded waveguide slow-wave structure is derived by the multi-conductor transmission line method. The simulation results by HFSS are in good agreement with the calculation results obtained from the dispersion equation. Influences of structure parameters on dispersion characteristics are discussed. It can be concluded that with the increase of inner conductor and the decrease of the period length, the bandwidth of the slow-wave structure becomes greater. The dispersion characteristics of the coaxial interlaced disk-loaded waveguide and those of the coaxial disk-loaded waveguide are compared. The results show that the coaxial interlaced disk-loaded structure can obtain a wide bandwidth and weak dispersion. This study will be a guide to the research of the coaxial interlaced disk-loaded waveguide slow wave structure used in the traveling-wave tube.