Abstract: 【Objective】 This study was amied to evalute the genetic diversity and genetic relationship of Liangshan black sheep population in Sichuan province,in order to provide scientific basis for the protection and rational utilization of local black sheep germplasm resources.【Method】 Mitochondrial cytochrome b (Cytb) gene of Liangshan black sheep was amplified by PCR and sequenced.The sequence length and mutation site information were confirmed by BLAST comparison.Combined with 153 sequences from 22 sheep breeds at home and abroad downloaded from GenBank,mitochondrial Cytb gene sequences of sheep were analyzed using Mega 7.0 software for base composition and genetic distance analysis,and DnaSP 5.0 software was used for genetic diversity analysis.【Result】 The Cytb gene size of Liangshan black sheep population was 1 140 bp,no insertion or deletion was found,and the AT content was higher than GC content.A total of 13 variation sites were found in the Cytb gene of 60 black sheep,with 13 haplotypes,of which H2 and H3 were the dominant haplotypes.The haplotype diversity (Hd),nucleotide diversity (Pi) and mean nucleotide variance (K) of Liangshan black sheep were 0.674,0.00120 and 1.371, respectively.Phylogenetic tree analysis showed that the genetic distance between Liangshan black sheep and Wula Black sheep was the smallest,and the genetic distance between Liangshan black sheep and Ovis ammon was the largest.【Conclusion】 The genetic diversity of Cytb gene in Liangshan local black sheep was low,and the genetic diversity of Cytb gene in Yanyuan black sheep was much lower than that in Butuo and Puge black sheeps.The three black sheep groups were closely related,and it was speculated that they had two matrilineal origins.Liangshan local black sheep had the closest relationship with Wula black sheep,but had a distant relationship with Ovis ammon.