The inter-conversion energy barrier for stable T_d structure of Li_4O to C_(2v) is calculated by ab initio theoretical method (MP4/6-31G°) to be 17.8 kcal/mol; while Na_4O molecule needs 19.4 kcal/mol for the similar process to take place. The variations of bond length, bond strength and electron population during the process of conversion are discussed in detail.