The effects of alkali metals on the oxidation of p-xylene (p-X) have been studied. The oxidation reaction is eventually promoted due to the alkali metal itself, even though the reaction is decelerated a bit in the beginning of the reaction. The promoting effect of alkali metal is not related to the basicity or to the anion. The effect increases as the concentration of Mn or Br decreases. The acceleration effect generally increases with the degree of deceleration in the beginning of the reaction. Through the analysis of products, one may understand that the alkali metal does not change the reaction mechanism.