An specific investigation has been carried out on the mechanism of the catalytic conversion of ethanol to 1,3-butadiene on magnesia-silica acidic-basic bifunctional catalysts. The magnesia-silica catalyst was prepared by wet-kneading and the reaction process was detected through Impulse Response and Diffuse Reflectance Infrared Fourier Transform Spectroscopy. The mechanism of 1,3-butadiene formation from ethanol was demonstrated through experiment in this time, and the process was proved as follows: Firstly, ethanol was dehydrogenated to form acetaldehyde; Then condensation of acetaldehyde formed acetaldol; Then dehydration of acetaldol to croton aldehyde; Finally, ethanol was involved a second time in a hydrogen transfer reaction with croton aldehyde to form 1,3-butadiene.