Abstract: A new standpoint is proposed for understanding the quantum phase transition from a higher-ordered excitation model to other lower-ordered one. It suggests that a nucleus populating at high-spin state is decoupled firstly to the yrast-band with the E2-trasitions mode, and then to the coexist region, wherein the structure-energy is released, the change of the nucleon coupling intensity is caused, finally the ground-states of the lower-ordered excitation model is reconstructed, the evolution of ground-state structure occurs. Microscopically, this is a benignancy and calm transition. In addition, an explanation is given to the possibility that two phase transitions can occur in some isotopes. A detailed discussion is presented with the 180, 182Hf nuclei as an example.