A nucleic acid extraction system, comprising an installation frame, a nucleic acid extraction plate, a plurality of nucleic acid extraction columns, a pipetting device and a positive pressure device, wherein the nucleic acid extraction plate is a plate configured to hold the plurality of nucleic acid extraction columns, each of the plurality of nucleic acid extraction columns is configured to receive a liquid and to extract or purify nucleic acids, the liquid is a solution including a nucleic acid solution to be extracted or chemical reagents, the pipetting device and the positive pressure device are arranged side by side, wherein the pipetting device comprises an infusion set, an infusion set mounting frame, an infusion set drive unit and a plurality of infusion units, the infusion set comprises sealed chambers which correspond to the plurality of infusion units in one-to-one correspondence, the sealed chambers are arranged side by side, a needle is provided on the bottom of each sealed chamber, each needle is in communication with the corresponding sealed chamber, the infusion set is arranged on the bottom of the infusion set mounting frame, and the infusion set drive unit is fixed on the installation frame and is configured to drive the infusion set to move up and down through the infusion set mounting frame; each infusion unit comprises a reagent supplier and a reagent flow controller, and in each infusion unit, a liquid outlet of the reagent supplier is in fluid communication with a liquid inlet of the reagent flow controller, and a liquid outlet of the reagent flow controller is in fluid communication with the corresponding sealed chamber; the positive pressure device comprises a plug, an air pipe, a positive pressure provider and a positive pressure drive device, the plug has an air pipe communicating hole, one end of the air pipe hermetically communicates with the air pipe communicating hole, and another end of the air pipe hermetically communicates with an air outlet of the positive pressure provider, and the positive pressure drive device is fixed on the installation frame and is configured to drive the positive pressure provider to move up and down; and the plurality of nucleic acid extraction columns are arranged on the nucleic acid extraction plate, the plurality of nucleic acid extraction columns are correspondingly arranged below the needles or the plugs, a liquid inlet of each nucleic acid extraction column has a sealing gasket which is in a sealing fit with the corresponding plug, and the nucleic acid extraction column is detachably and hermetically connected with the corresponding plug. wherein the pipetting device comprises an infusion set, an infusion set mounting frame, an infusion set drive unit and a plurality of infusion units, the infusion set comprises sealed chambers which correspond to the plurality of infusion units in one-to-one correspondence, the sealed chambers are arranged side by side, a needle is provided on the bottom of each sealed chamber, each needle is in communication with the corresponding sealed chamber, the infusion set is arranged on the bottom of the infusion set mounting frame, and the infusion set drive unit is fixed on the installation frame and is configured to drive the infusion set to move up and down through the infusion set mounting frame; each infusion unit comprises a reagent supplier and a reagent flow controller, and in each infusion unit, a liquid outlet of the reagent supplier is in fluid communication with a liquid inlet of the reagent flow controller, and a liquid outlet of the reagent flow controller is in fluid communication with the corresponding sealed chamber; the positive pressure device comprises a plug, an air pipe, a positive pressure provider and a positive pressure drive device, the plug has an air pipe communicating hole, one end of the air pipe hermetically communicates with the air pipe communicating hole, and another end of the air pipe hermetically communicates with an air outlet of the positive pressure provider, and the positive pressure drive device is fixed on the installation frame and is configured to drive the positive pressure provider to move up and down; and the plurality of nucleic acid extraction columns are arranged on the nucleic acid extraction plate, the plurality of nucleic acid extraction columns are correspondingly arranged below the needles or the plugs, a liquid inlet of each nucleic acid extraction column has a sealing gasket which is in a sealing fit with the corresponding plug, and the nucleic acid extraction column is detachably and hermetically connected with the corresponding plug.