The invention discloses a method for preparing rehmannin B, rehmannin D and jioglutin A. The method comprises the following steps: step S1, carrying out water extraction on fresh rehmannia sheets withethyl alcohol, and carrying out vacuum concentration to obtain an extract; step S2, dissolving the extract with water, firstly extracting with petroleum ether, and then extracting with dichloromethane to obtain a dichloromethane extract; step S3, loading XDA-1B macroporous resin with the dichloromethane extract for carrying out sample loading, firstly carrying out decontamination with 30% ethyl alcohol, then carrying out elution with 75% ethyl alcohol, collecting 8 to 10 BV eluant, and concentrating the eluant to obtain a rehmannin extract crude product; step S4, loading a normal phase silicagel column with the rehmannin extract crude product for carrying out sample loading, then carrying out elution with a mixture of dichloromethane, methyl alcohol and isopropanol in the volume ratio of10:1:0.2, collecting 6 to 7 BV eluant, and concentrating and drying the eluant to obtain a rehmannin extract; step S5, separating the rehmannin extract with a preparation solution, and collecting thecorresponding ingredients of rehmannin B, rehmannin D and jioglutin A according to a chromatogram map; and step S6, desalination: carrying out desalination on the corresponding ingredients of rehmannin B, rehmannin D and jioglutin A to obtain rehmannin B, rehmannin D and jioglutin A.