Abstract: Based on the dispersion relation of double combed slow-wave structure, we analyzed and discussed the dispersion characteristics of positive and negative symmetric mode of the electric field in detail, and studied the empty of slow wave, waveguide height and depth of the slow wave effect on the dispersion characteristics. Contrasted with the effects on the positive and negative symmetric mode by changing various parameters, it is concluded that only in reducing the waveguide height and maintain slow-wave depth does not decrease, can we increase frequency isolation between the positive and negative symmetrical pattern.