This work presents an approach to realize the dispersion engineering of spoof plasmonic metamaterials with controllable cutoff frequencies. Interdigital capacitance structures are applied to construct the unit cells. Dispersion properties are firstly analyzed to investigate the effects of interdigital capacitance, and the influence of the geometrical parameters of the proposed unit cell on the cutoff frequencies is studied. Then, a spoof surface plasmon polariton (SSPP) transmission line (TL) is developed based on the proposed unit cell together with a smooth transition. The matching principles of the transition are explained by the dispersion curves and the normalized impedance of the corresponding matching unit cells. Finally, the transmission characteristics of the TL are simulated and measured to validate the feasibility of the proposed strategy. Both the lower and upper cutoff frequencies can be tuned jointly by the extra degrees of freedom provided by the interdigital capacitance structures. In comparison with designs based on a substrate-integrated waveguide (SIW), the proposed strategy can reduce the transversal dimension by a factor of two under the same conditions. This work can greatly accelerate the development of versatile microwave integrated circuits and systems based on spoof plasmonic metamaterials.