Based on the algebraic method (AM) proposed to calculate accurate full vibrational energies for diatomic molecules in Sun’s previous work, the parameter-free analytical formula for dissociation energy of diatomic system is used to study the dissociation energies and the full vibrational spectra of 5 electronic states of Li2 molecule in this work. The results show that the AM vibrational spectra and dissociation energies are in excellent agreement with experimental results.