AKR1B10 is a human NADPH-dependent aldo-keto reductase family 1 B10, which has been considered as a potential cancer therapeutic target. 3,5-O-Dicaffeoyl-epi-quinic acid (3,5-DCQA) was isolated from ethyl acetate fraction of Gymnaster koraiensis (Nakai) Kitam as an AKR1B10 inhibitor. 3,5-DCQA inhibited the activity of recombinant human AKR1B10 (rhAKR1B10) with its $IC_{50}$ value of $1.2;{mu}M$ and its inhibition mode was uncompetitive from enzyme kinetic analysis.