An experiment of the preparation of mono-ethanolamine, die-ethanolamine, and tri-ethanolamine from aqueous ammonia and ethylene oxide is studied. In the reaction system, water carries out the catalysis. The activation energy of mono-ethanolamine is determined, 61.52kJ.mol-1. The frequency factor is a quadratic function of water concentration. Under different reaction temperature, three final ethanolamine product contents are constant, which indicate the activation energies of three ethanolamins are equal. Using nonlinear least square regression, reaction rate ratios of die-ethanolamine or tri-ethanolamine to mono-ethanolamine are calculated. The two ratios are both linear relation with water concentration, dropping with water concentration increase.