The large-scale network environment incarnates interconnection of different security domains. There are different security policies in the domain or among the domains, and conflicts can arise in the set of policies which lack of trust and consultation. A network security policy model is proposed in this paper. By defining and describing security policy and domain, the policies’ integrity, validity, consistency, conflicts detecting, resolving and releasing are studied. The policy implementation mechanism is based on rule engine. This paper gives the achieve steps and efficiency analysis. The technology can be adapted to establishing and controlling the policy service in the extensive network environment.