[Objective] The aim of this paper was to investigate the genetic diversity of mitochondrial DNA D-loop sequences of Cheilinus undulatus populations.[Method] Twenty-five individuals of C. undulatus were collected from the offshore area of Hainan Province. PCR and cloning techniques were used to clone and purify the mtDNA D-loop sequences of C. undulatus populations( n = 25),about 1 400 bp long PCR product was obtained. ClustalX software was adopted for sequence alignment,and results were imported into MEGA5. 0. [Result] According to experimental results,66 mutation sites were detected from 25 individuals,including 0 deletion,4 inserts,59 transition sites,2 transversion sites and 1 transition-transversion site. Pairwise genetic distances of these 25 individuals were calculated by using MEGA5. 0 software. Based on that,NJ phylogenetic tree of these 25 individuals was constructed. Analysis of C. undulatus populations using DNASP software showed that the polymorphic site number( S) was 62,nucleotide diversity(Pi) was 0. 006 06,and average number of nucleotide differences(K) was6. 907. [Conclusion] Overall,there was no significant variation among mtDNA D-loops of C. undulatus populations. [Objective] The aim of this paper was to investigate the genetic diversity of mitochondrial DNA D-loop sequences of Cheilinus undulatus populations. [Method] Twenty-five individuals of C. undulatus were collected from the offshore area of ​​Hainan Province. PCR and cloning Techniques were used to clone and purify the mtDNA D-loop sequences of C. undulatus populations (n ​​= 25), about 1 400 bp long PCR product was obtained. ClustalX software was adopted for sequence alignment, and results were imported into MEGA5.0 . [Result] According to the experimental results, 66 mutation sites were detected from 25 individuals, including 0 deletion, 4 inserts, 59 transition sites, 2 transversion sites and 1 transition-transversion site. Pairwise genetic distances of these 25 individuals were calculated by using Analysis of C. undulatus populations using DNASP software showed that the polymorphic site number (S) was 62, n ucleotide diversity (Pi) was 0. 006 06, and average number of nucleotide differences (K) was 6. 907. [Conclusion] Overall, there was no significant variation among mDNA D-loops of C. undulatus populations.