A continuous flow catalytic reactor, an assembling method therefor and an application thereof includes a reaction vessel, a filler packaged in the reaction vessel and a charged catalytic component; the charged catalytic component is fixed to the filler under an action of a direct-current electric field. The continuous flow catalytic reactor may be applied to continuous flow reactions such as a monosaccharide epimerization reaction. A monosaccharide epimerization reaction method includes: providing the continuous flow catalytic reactor; electrically connecting the continuous flow catalytic reactor with a direct-current power supply, thereby to forming the direct-current electric field by electrically connecting the continuous flow catalytic reactor with the direct-current power supply; and heating a reactor container to a target temperature, and inputting a monosaccharide solution from a liquid flow inlet of the reaction vessel and then collecting a solution containing a target product from a liquid flow outlet of the reaction vessel.