A Laugmuir-Hinshelwood type kinetic model of ethyleneimine (EI) formation by vapor phase dehydration of monoethanolamine over an acid-base catalyst was derived. By using this model, the extraordinary behavior of this reaction was explained as follows: EI formation reaction was restricted by equilibrium, but side reactions were not restricted. When monoethanolamine was converted at a level higher than the equilibrium Of the main reaction, FA selectivity was theoretically restricted. A reaction process was designed by use of this model, and a reduced pressure process Without carrier gas was proposed.