In this research, the quantum phase transition (QPT) in the Casten pyramid has been investigated using entanglement entropy. Energy surfaces and the entanglement entropy have been obtained within the framework of semi-classical approximation, interacting boson model-2 (IBM-2), using Schmidt decomposition and coherent states formalism. The results showed that the entanglement entropy is a suitable and efficient tool for investigating QPT and determining critical points in the connected pathes to the Uπν (5) limit, and pathes of SUπν (3) ↔ Oπν (6) ↔ SUπν (3) and SU∗πν (3) ↔ Oπν (6) ↔ SU∗πν (3). The description of QPT using numerical analysis of energy surfaces confirms the results of entanglement entropy.
