An H7 avian influenza vaccine strain which differentiates infected from vaccinated animals, a preparation method therefor, and an application. The highly pathogenic H7 avian influenza not only brings about huge economic losses to the livestock industry, but also seriously threatens public health safety. Conventional H7 avian influenza whole virus inactivated vaccines do have advantages such as being reliable in terms of effect, low in terms of cost and wide in terms of application range, but cannot serologically differentiate infected from vaccinated animals. The present invention uses NA of influenza B as a label to establish a method for constructing an H7 avian influenza vaccine strain which differentiates infection from vaccination, and may be used for the prevention, control and decontamination of the H7 avian influenza.
