The invention belongs to the technical field of food quality and safety detection, and particularly relates to a PCR detection method for identifying duck meat mixed in mutton. A universal upstream primer F and two specific downstream primers R sheep and R duck are designed with mitochondrial cytochrome b gene of mutton and duck meat as characteristic target gene, a primer mixture is formed according to a certain concentration ratio, specific amplification fragments with different lengths can be obtained through one-time PCR, and analysis is conducted according to the size of molecular weight of strips obtained through electrophoresis detection. If specific strips appear on a sample to be detected at the positions of 367bp and 480bp, it proves that duck meat is mixed in the mutton sample; if specific strips appear on the sample to be detected at the position of 367bp and do not appear at the position of 480bp, it proves that no duck meat is mixed in the mutton sample. The method is accurate, reliable, simple and quick and can be used for screening species of meat in food and detecting and supervising meat adulteration.