[Objective] The study aimed to establish a fast and accurate method to detect the polymorphism of the 12^th exon of equine MxA gene. [Method] The 12^th exon of MxA gene was amplified by mismatch PCR and the products were analyzed by restriction fragment length polymorphism （RFLP） to determine the point mutation at the 1 790 nt of MxA cDNA. The sequence of the PCR products was also analyzed. [Result] There were three genotypes （AA, AB and BB） in the 12^th exon of equine MxA gene; the 2 081 nt of MxA cDNA mutated from G to C, correspondingly changing the 562^th amino acid of the coding region of MxA protein from tryptophan to cysteine; the specific sequence of the PCR products amplified by mismatch PCR-RFLP was consistent with the analysis results of RFLP. [ Conclusion] The mismatch PCR-RFLP was an easy method with accurate results to detect the polymorphism of the 12^th exon of equine MxA gene.
