High seafood demand in the supply chain often leads to seafood mislabelling , where the supplier substitutes higher commercial value fish species with less valuable ones. Thus, having an effective method for species identification is crucial to reduce mislabelling of common fish and fishery products . Besides morphological feature identification, many DNA-based species identification methods using the biomarker have been developed. As compared to nuclear DNA, mitochondria DNA (mtDNA ) is more favourable as it is a circular genome that exhibits maternal inheritance, has higher copy numbers per cell for easy isolation and evolves faster which allows identification of closely related species easier. In this study , a mitochondria gene, Cytochrome c Oxidase Subunit I (COI ) was chosen as a DNA biomarker for species identification. U niversal biomarkers were developed to identify fish species and fish commercial products that are commonly sold in the Taiwan market. The genomic DNA of fish species was extracted and amplified to ensure accurate PCR amplification of the t arget region. Based on the results, the universal biomarker can amplify the COI targeted region of more than 10 fish species. Besides, to mimic the manufacturing process of the fish commercial products, samples were treated under various heat and pressure conditions to observe the DNA stability. The results showed that the denatured DNA can still be amplified after high-temperature and pressure treatment. Moreover, species identification was studied by using species-specific COI primer to carry out multiplex PCR . This PCR amplification technique is a rapid and lower-cost identification method for species identification based on the size variation of the target region . To conclude, this study showed that both universal and specific biomarker works well for species identification, which provides insight for future research in species identification to reduce seafood mislabelling .