Abstract: Newcastle disease is one of poultry infectious diseases caused by Newcastle disease virus. Maxingshigan Tang has the obvious therapeutic effects to the respiratory disease, also has the function of antivirus and the bacteriostasis. By four different doses of the medicine group of Maxingshigan Tang, using the decoction method extracted the medicine active ingredients. By determining the extract to the chicken embryo's maximum lethal concentration and hemagglutination. By different medicine liquor concentration direct action in virus, inoculate embryo determine the change of virus titer, found that all 8 compoundings have the effect of antivirus, and Mahuang is the essential component. Medicine has no directly relation in both antivirus and hemagglutination.