The invention relates to a device and method for separating methyl alcohol and ethanol from the hydrocracking product of stalk sugar; the device consists of a light component removal tower, a dehydration column and a methyl alcohol and ethanol separation tower; the gas phase pipeline on the top of the light component removal tower is connected with the reboiler of dehydration column and reboiler of methyl alcohol and ethanol separation column respectively to condense and recover the aqueous solution of methyl alcohol and ethanol; the aqueous solution of methyl alcohol and ethanol then goes to the dehydration column to have the moisture removed further; the methyl alcohol and ethanol recovered on the top of the dehydration column goes to the methyl alcohol and ethanol separation tower; then methyl alcohol can be obtained from the top of the methyl alcohol and ethanol separation tower, and ethanol can be obtained from the bottom of the methyl alcohol and ethanol separation tower; the only steam source to the three towers is to heat the reboiler of the light component removal tower; then the steam generated by the light component removal tower can heat the reboiler and the reboiler of the methyl alcohol and ethanol separation column. Operating pressure of the light component removal tower is higher than the operating pressure of the dehydration column and methyl alcohol and ethanol separation tower, as a result of which, difference between the temperature of gas phase on the top of the light component removal tower and the temperature of reboiled gas phase of the dehydration column and methyl alcohol and ethanol separation tower kettle is above the minimum thermal temperature difference, and the heat given out by condensation on the top of the methyl alcohol and ethanol separation tower matches with the heat required for reboiling of the dehydration column and methyl alcohol and ethanol separation tower kettle.