The invention discloses a method for purifying
RNA (ribonucleic acid) in a biological sample by a selective
filtration column. The method specifically comprises the following steps of centrifuging anddelaminating the biological sample treated by an
RNA lysis buffer at high speed, adding an upper water phase into an inner tube of the selective
filtration column, and centrifuging the selective
filtration column in a centrifuging
machine; adding 5 to 100 microliters of water into the inner tube of the selective filtration column, oscillating for 30s, and transferring a water solution in the inner tube of the selective filtration column into a
centrifuge tube without
RNA enzyme, wherein the solution in the
centrifuge tube is the purified RNA solution; enabling the RNA
lysis buffer to lyse thecells of the biological sample, centrifuging and delaminating at high speed, removing
cell fragments and
DNA (deoxyribonucleic acid), enabling the RNA to completely dissociate in the upper water phase, and enabling the RNA to pass through a bottom
ultrafiltration membrane of the selective filtration column, wherein the
ultrafiltration membrane only has permeability on micromolecular substances and no permeability on RNA of biological macromolecular substance under the high-speed centrifuging condition, so as to realize the purifying of the RNA of the biological macromolecular substance.