The influence of Li-rich vapor transport equilibration (VTE) on surface Li2O-content of 1-mm-thick, congruent X-, and Z-cut LiNbO3 crystal plates was studied against the VTE temperature. The VTE-induced surface Li2O-content increase was evaluated from measured birefringence. The results show that the increase follows the traditional Arrhenius law with a surface Li2O-content alteration constant (614 +/- 136)/(91 +/- 10) mol% and an activation energy (0.76 +/- 0.05)/(0.53 +/- 0.03) eV for the X/Z-cut plate. An empirical expression that correlates the VTE-induced surface Li2O-content alteration with both the VTE temperature and duration is presented. The expression is useful for producing a near-stoichiometric LiNbO3 plate with the desired surface Li2O-content via balancing the VTE temperature and duration.