With the development of nuclear power, nuclear power plant safety and emergency management work has aroused great concern of society. Addressing nuclear power plant accidents (NPPAs) overwhelms the capability of single jurisdictional government and spans the boundaries of multiple sectors. However, there is still a lack of research on the antecedent condition, the process mechanism, the basic elements and components of the cross-organization collaboration in the field of NPPAs emergency management in off-site area. On the basis of the initial theory, basic elements and constituent elements of cross-organization collaboration, this article will define the cross-organization collaboration process as a system process interacted with the environment, which consists of four basic elements of collaborative condition, collaborative process, collaborative structure, and collaborative output. Based on the description and analysis of the case of S City, with the explanation of the basic element, the constituent elements and the collaboration mechanism, this article proposes a cross-organization collaboration framework including collaborative antecedents, collaborative process, collaborative structure, collaborative governance and collaborative outcome of NPPAs emergency management in off-site area.