Mystus guttatus is one of four famous fishes m the Pearl River, but the population depression is repaidly rapidly in recent years, and fishing resource needs protection.1137 nucleotides of mitochondrial Cytochrome b gene sequence(number: MGGD) have been obtained from Chinese bagrid fish Mystus guttatus, the contents of T、C、A、G of the gene are 31.6%、25.7%、29.6 %、13.1%respectively.Respectively compared to other two sequences from GenBank(number: MGZJ,MGFJ), the gene sequence divergence of M.guttatus among the three sequences is 0.005 to 0.017.The difference of amino acid sequences converted by gene sequences are all only 2 sites, so it shows that Cytb gene which acts as a functional gene is conservative.And value of transition is larger than value of transversions in Mystus fishes.The research is aimed to offer some genetic data of M.guttatus for fishing resource protection and genetic selection, and the structure of Mystus guttatus population need be further researched.