The conserved polyad number of DCO vibration is employed to classify its highly excited vibrational states. The dynamical potentials are shown to be anti-Morse and harmonic along the D-C and C-O coordinates, respectively. These, together with the Lyapunov and phase space analyses, are demonstrated to interpret the state stability that in the lower energy realm according to a polyad, D-C is prone to be dissociative or chaotic while the states in the very high energy realm, are stable and regular. A model of a particle moving in an anti-Morse potential and coupled to a simple harmonic oscillator is established for DCO vibrational dynamics. (C) 2007 Elsevier B.V. All rights reserved.