China is abundant of sheep genetic resources. A total of 55 sequences containing the Ovis aries mtDNA D: -loop of three large-fat-tailed sheep breeds, named Lanzhou, Tong, and Han were retrieved from GenBank to investigate their genetic diversity, origin, and phylogenetic evolution. The results showed that the sheep breeds in our study proved to be extremely diverse, the average haplotype diversity and nucleotide diversity were 0.987 ± 0.006 and 0.03956 ± 0.00206, respectively. The 55 sequences gave 39 different haplotypes. Phylogenetic analyses revealed that there were three distinct mtDNA haplogroups: A, B, and C, in which haplogroup A was predominant and had experienced population expansion events. Clustering analysis showed that the large-fat-tailed sheep breeds clustered into one group and were closely related to the Mongolian sheep and then European mouflon sheep (Ovis musimon). The results contribute to the knowledge of Chinese sheep breeds and the plan of conservation programs on large-fat-tailed sheep.