Transformation mechanism of ethanol into acetone over zinc-calcium oxide catalyst  has been studied. It is established that products of transformation of ethanol are acetone, acetaldehide, carbon dioxide and various hydrocarbons. For definition of a way of formation of acetone a number of researches of joint transformation of ethanol with acetic acid, acetaldehide with ethylene, acetaldehide with acetic acid has been carried out. It is shown that in reactions of joint transformation of ethanol with acetic acid and acetaldehide with acetic acid acetone is formed in small amounts. It is found out, that the greatest quantity of acetone is formed at interaction acetaldehide with ethylene. The conclusion is drawn, that ethanol turns to acetone through a formation stage of surface acetaldehide-ethylene complex. On the basis of the received data the phasic scheme of transformation of ethanol in acetone is offered