Ethanol decomposition on a platinum cluster is investigated by ab initio MD simulation. As the dehydrogenation proceeds, the Mulliken charge of the methylene carbon becomes a positive value, whereas that of the methyl carbon keeps a negative value. Especially, the Mulliken charge of the methylene carbon in CHxCO (x=0, 1, 2 and 3) fragment molecules takes a large positive value. These fragment molecules correspond to those with C-C bond that dissociated in the MD simulation. It suggests the large deviation in the Mulliken charge between methylene and methyl carbons is the key factor inducing the C-C bond dissociation. (C) 2015 Elsevier B.V. All rights reserved.