The utility model provides a chromatographic column. The chromatographic column comprises at least two different solid layers. For an example, a double-layer chromatographic column is composed of a first solid layer and a second solid layer which are connected in series and coupled, the first solid layer is composed of an anion exchange membrane or microbeads, and the second solid layer is composed of a silica gel film or microbeads. The chromatographic column is simple in structure, easy to use and especially applicable to coseparation of RNA (ribonucleic acid) and DNA (deoxyribonucleic acid), extraction of nucleic acid coated with proteins, like viruses, and separation of nucleic acid with a large volume and low concentration, like a small amount of nucleic acid extracted from plasma; the extracted nucleic acid can be directly put in downstream applications.