The unanalytical feature of the Mott–Hubbard metal-insulator transition in infinite dimensions is studied by using a modified self-consistency scheme in the framework of dynamical mean-field theory. For a specific low temperature T=0.0025W (W: half bandwidth), the "Z"-shaped or "S"-shaped curves for double occupancy D, energy per lattice site E, and the quasi-particle weight Z are obtained as functions of U. Direct observation shows that the Fermi-liquid phase changes to the insulating phase through a non-Fermi-liquid phase at the unstable level. Based on our results, a scenario of zero temperature MIT is proposed. The phase diagram for MIT on the T–D plane is also presented.