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Firewalls are core elements in network security, the effectiveness of firewall security is dependent on configuring firewall policy correctly.Firewall policy is a lower-level policy which describes how firewall actually implements security policy. Security policy is a higher-level policy which defines the access that will be permitted or denied from the trusted network. Compare with software engineer, security policy is a design, firewall policy is a set of codes. It is useful to discover inconsistency between security policy and firewall policy. In this paper, we present a method of verifying consistency between security policy and firewall policy, which applies the idea of model checking. First of all,two policies and the consistency are represented with logic programs. Then the verification is applied by testing whether the logic formula of the consistency is satisfied in the semantics of the logic programs. Furthermore, We prove that the method has an unique answer which can be computed in polynomial time.