In this paper, the MgO-SiO2 catalyst was prepared with the deposition-precipitation method, which was used to catalyse the conversion of ethanol to 1,3-butadiene through a two-step process. The carbon deposition deactivation of the catalyst was mainly caused by that the carbon species occupied the acid-basic active sites on the catalyst surface. The carbon deposition mainly includes chain alkanes and aromatic compounds from outer to inner layers, and its site was mainly MgSiO3, followed by MgO, while SiO2 showed weak carbon deposition ability. Graphic