Abstract: The present invention concerns a method for directly synthesizing acrolein or methacrolein from a mixture of methanol and ethanol or propanol. The method of the invention comprises two successive phases: oxidation in the presence of a selective oxidation catalyst of the light alcohols of the feedstock, then condensation by aldolisation of the aldehydes formed during oxidation in the presence of a condensation catalyst (aldolisation). Alternatively, the two phases can be carried out in the presence of a single catalyst, in particular in the presence of a molybdenum-based selective oxidation catalyst. These two phases can be conducted in a single reactor or in two cascade reactors.