The invention relates to a preparation method for hypoglycemic active ingredients in radix rehmanniae recen and specifically relates to a method for preparing two active ingredients which are shown ina formula I and a formula II at the same time. The preparation method is characterized by comprising the following steps: (1) taking the radix rehmanniae recen, smashing to 20 to 80-mesh particles and performing supercritical CO2 extraction to obtain crude extract; (2) dissolving the crude extract obtained in the step (1) by ethyl alcohol of 2 to 3 times of mass, adsorbing by macroporous resin, eluting by ethyl alcohol with a volume fraction of 50 to 70%, collecting eluate of 3 to 5 times of the column volume, performing vacuum concentration, performing Sephadex LH-20 gel column chromatography, collecting eluate of 2 to 3 times of the column volume, performing vacuum concentration and obtaining two active ingredients which are shown in the formula I and the formula II by high performanceliquid chromatography preparation, wherein an eluent is a CHCl3/MeOH mixed solvent with a volume ratio of 1 to 1.