Abstract：The density functional theory B3LYP/6-31G(d,p) was employed to study the mechanism of aminolysis of phenyl formate with ammonia in gas phase. Two reaction pathways, the concerted and the stepwise pathways were considered through neutral intermediates. The effect of various solvents such as water, ethanol and acetonitrile on the title reaction was assessed by the polarizable continuum model. The calculated results show that the neutral concerted pathway is the most favorable one in the gas phase and solutions. The reduction of energy of activation in the concerted path of the aminolysis of phenyl formate was found to be more significant than that in the neutral stepwise process due to the solvent effect of water, ethanol and acetonitrile. The solvation effect of different solvents was not sensitive to their polarities in this reaction of phenyl formate with ammonia.