Abstract: A method for liquefying and saccharifying starch quickly includes the steps of: irradiating starch with 0.25×106˜1.5×106 Gy 60Co-? rays or electron accelerator, putting the irradiated starch into a fermenting tank and adding cold water, stirring mechanically to forma solution, adding a little amount of starch saccharifying enzyme to saccharifying the starch under acid condition.