In order to get high quantity and quality animal-derived DNA extraction from processed food, the CTAB method was improved for the PCR test. According to duck mitochondrial gene sequences, primers were designed and synthesized for detecting PCR system, optimizing reaction conditions and screening, establishing a triple PCR method. The amplified lengths of fragments were 116 bp for bovine, 212 bp for porcine, 322 bp for duck, respectively. The triple PCR assay to distinguish pork and duck from beef was developed. Lower amounts of meat than declared on the label. These practices are of great importance in the fight of forged food, examining the food labels, protecting the right to know and the health concern of consumers.