Abstract: A new kind of slow-wave circuit, tunnelplane, is put forward. The tunnelplane circuit was similar to tunneladder slow-wave circuit, but the support between the ring and the metal wall is a metal plane. The tunnelplane was analyzed by field method. The discrepancy of dispersion between the analysis and CST was within 1.5%. The analysis shows that the tunnelplane structure has relatively broader band than the tunneladder structure, and both of the structures have high interaction impedance.