The invention discloses a method for extracting and purifying target nucleic acid and an application thereof. The extraction method comprises a marker B and a specific conjugate A, wherein, capturing nucleic acid marked by the marker B and target nucleic acid in sample are combined to a solid phase carrier combined with the marker B and the specific conjugate A to form a compound of capturing nucleic acid- target nucleic acid of solid phase carrier-A-B; and the capturing nucleic acid at least comprises a 2`-oxygen-methylation oligoclonal nucleic acid which is specifically combined with the target nucleic acid RNA and is marked by the marker B. The invention also provides a kit for extracting the target nucleic acid, which at least comprises a 2`-oxygen-methylation oligoclonal nucleic acidwhich is specifically combined with the target nucleic acid RNA and is marked by the marker B, and the 2`- oxygen- methylation oligoclonal nucleic acid is used as the capturing nucleic acid. The method has the advantages of high specificity and purity, less pollution, constant temperature in the reaction process, high sensitivity, fast detecting speed, low requirements on instruments and low cost. Thus, the method is particularly applicable to blood screening.