The quasiparticle interferences (QPIs) of the featureless Mott insulators are investigated by a T -matrix formalism implemented with the dynamical mean-field theory (T -DMFT). In the Mott insulating state, due to the singularity at zero frequency in the real part of the electron self energy (ReΣ(ω) ∼ η/ω) predicted by DMFT, where η can be considered as the 'order parameter' for the Mott insulating state, QPIs are completely washed out at small bias voltages. However, a further analysis shows that ReΣ(ω) serves as an energy-dependent chemical potential shift. As a result, the effective bias voltage seen by the system is eV ′ = eV − ReΣ(eV ), which leads to a critical bias voltage eVc ∼ √ η satisfying eV ′ = 0 if and only if η is non-zero. Consequently, the same QPI patterns produced by the non-interacting Fermi surfaces appears at this critical bias voltage eVc in the Mott insulating state. We propose that this re-entry of non-interacting QPI patterns at eVc could serve as an experimental signature of the Mott insulating state, and the 'order parameter' can be experimentally measured as η ∼ (eVc)2 .