Objective The aim was to provide basis for molecular marker assisted selection and resistance breeding of Langya chicken. Method The genetic polymorphism of Hae III site of Mx gene 3＇ sequence in Langya chicken was analyzed by PCR-RFLP. Result The results showed that Hae III site controlled by allele A and B were polymorphic in Langya chicken breeds and the allele frequencies of A and B were 0.562 and 0.438 respectively. The genotype distribution of Hae III site was significantly not in Hardy-Weinberg equilibrium （ P 〈0.01 ）. The polymorphic fragments were cloned and sequenced, and the results revealed that the fragment size was 357 bp and a deletion of 31 bp occurred in variation sequences. Conclusion It was found that Hae III-RFLP exists in Mx gene 3＇ sequence in Langya chicken breeds of Shandong Province.
