This study investigates reaction kinetics of high-pressure amination of polyalkylene glycol (PAG) to polyetheramine (PEA). The reductive amination of PAG was carried out depending on the NH3 amount, reaction temperature, reaction pressure, and H2O content in a batch reactor to understand the effect of these factors on activity and selectivity toward the primary amine. Contrary to the fact that the amination step is a zero-order reaction and dehydrogenation of alcohol to ketone is the rate-limiting step in the reductive amination of alcohol, the amount of NH3 significantly affected the reaction rate. The increased amount of NH3 enhanced the activity and selectivity for PEA, in contrast with the results reported in prior studies. A Langmuir-Hinshelwood kinetic model was established to reflect the effect of the NH3 amount, and kinetic parameters such as the rate constant and activation energy were obtained at a high pressure around 150 bar. It was also found that the absence of NH3 caused the reverse reaction of PEA to the secondary amine in the presence of H2. The fundamental kinetic analysis provides a competitive synthesis route for improving the activity and selectivity toward the primary amine.