The invention discloses a kind of new reactive extraction technology to distill the low-grade polyhydric alcohol from the thin aqueous solution. The reactive extraction technology is a kind of new reactive extraction technology with the same material as the reactant and extractant, makes the aldolisation occur between the polyhydric alcohol and aldehyde to produce the cyclic acetal. It chooses the aldehyde which can partially resolve into water as the reactant as well as extractant, thus don't need to introduce into a new organic solvent and has simple technique. The boiling point of the chosen aldehyde is lower than that of water. Thus when we use the evaporation or rectification to reclaim the aldehyde from the extract phase, the aldehyde can be got from the fraction, which costs less energy, keeps the impurities of the water phase in the water to be separated and is more important to the complex system with large amount of impurities, such as fermentation broth.