The highly excited vibrational states of quasi-linear tetraatomic molecule HCNO are studied in the framework of U(4) algebra. By using symmetric group with which the tetraatomic molecules satisfy, we construct the algebraic Hamiltonian that not only includes Majorana operator M 12 but also M 13 and M 23 which are very useful for getting potential energy surface and force constants in Lie algebra method. And the eigenvalue of the Hamiltonian are obtained by Lie algebra treatment.
