Abstract: Immunohistochemistry methods using monoclonal antibodies (McAb) to diagnose Newcastle Disease (ND) have been established.The NDV antigen were found in the organs and tissues of the chickens infected NDV by using these methods. The FA positive rates of the spleen, lung, kidney, and caecum of the cnickens with ND were 86~91%, 91~93%, 100%, 86% respectively, which proved these organs were ideal tested samples for detecting NDV.In a comparison, the positive rate of FA(92.3%) was higher than the rate of virus isolation (87.2%), The concordant rate of the two nctiods was 89.7%.The results showed that the immunohistochemistry methods were simple,rapid and accurate,and that the McAb as a diagnosis reagent was excellent.