The invention belongs to the technical field of molecular genetics, and particularly relates to an SNP (Single Nucleotide Polymorphism) marker for identifying the weaning weight of alpine merino and application of the SNP marker, and the SNP molecular marker is located at the 3566034th nucleotide site C / T mutation on the 23rd chromosome of the international sheep reference genome Oarv4.0 version. The invention further relates to a specific primer pair for detecting the SNP molecular marker by using a PCR technology, a kit containing the primer pair and a nucleotide polymorphism detection method, and compared with a traditional detection method, the technology has the advantages of high accuracy, high detection speed, low cost, easiness in result judgment and the like. SNP locus detection is used for carrying out early selection of the weaning weight of the high-mountain merino sheep, shortening the breeding period and accelerating the breeding process, a technology for early selection of the weaning weight of the high-mountain merino sheep is established, the breeding time of excellent characters of the weaning weight of the high-mountain merino sheep is shortened, the breeding cost is reduced, and the application value is very high.