Highly excited vibrational dynamics of phosphaethyne (HCP) integrable system are investigated based on its dynamic potentials. Taking into consideration the 2:1 Fermi resonance between H-C-P bending vibrational mode and C-P stretch-ing vibrational mode, it is found that the effects of H-C stretching vibrational mode on vibrational dynamic features of the HCP integrable system are significant and regularly vary with Polyad numbers (P number). The geometrical profiles of the dynamic potentials and the corresponding fixed points are sensitive to the variation of H-C stretching vibrational strength when P numbers are small, but are not sensitive when P numbers become larger and the corresponding threshold values become lower. The phase space trajectories of different energy levels in a designated dynamic potential (P=28) were stud-ied and the results indicated that the dynamic potentials gove the various dynamic environments in which the vibrational states lie. Furthermore, action integrals of the energy levels contained in dynamic potential (P=28) were quantitatively analyzed and elucidated. It was determined that the dynamic environments could be identified by the numerical values of the action integrals of trajectories of phase space, which is equivalent with dynamic potentials.