The invention belongs to the fields of genetic breeding of animals, SNP markers and application, and particularly relates to an SNP marker and a molecular marker significantly related to Australian white sheep wool thickness and application. The molecular marker nucleotide sequence is shown as SEQ ID NO:1, an A/G allele mutation exists at a basic group of the position 111 of the sequence, and whenthe nucleotide at the position 111 of SEQ ID NO:1 is G, the hair of Australian white sheep is thicker. The invention also discloses a preparation method of the molecular marker related to the Australian white sheep wool thickness and application of a correlation analysis method thereof. A new SNP molecular marker is provided for molecular marker-assisted selection of thick wool traits of Australian white sheep, and the SNP molecular marker can be used for selective breeding and early selection of new Australian white sheep strains and in the process of breeding new Australian white sheep varieties by using Australian white sheep, so that the selection accuracy can be improved, and the breeding and purification progress can be accelerated.