  In this paper, the electronic properties of 30{\deg} twisted double bilayer
graphene, which loses the translational symmetry due to the incommensurate
twist angle, are studied by means of the tight-binding approximation. We
demonstrate the interlayer decoupling in the low-energy region from various
electronic properties, such as the density of states, effective band structure,
optical conductivity and Landau level spectrum. However, at Q points, the
interlayer coupling results in the appearance of new Van Hove singularities in
the density of states, new peaks in the optical conductivity and importantly
the 12-fold-symmetry-like electronic states. The k-space tight-binding method
is adopted to explain this phenomenon. The electronic states at Q points show
the charge distribution patterns more complex than the 30{\deg} twisted bilayer
graphene due to the symmetry decrease. These phenomena appear also in the
30{\deg} twisted interface between graphene monolayer and AB stacked bilayer.
