The present invention provides a DNS security system and failure processing method. The DNS security system comprises: at least one client, configured to initiate a DNS request; a root node, configured to provide authorization information to the DNS request; an authorization information database, configured to store all DNS requests and corresponding authorization information in a designated area; a virtual root node, configured to invoke corresponding authorization information from the authorization information database when a DNS resolution failure occurs on the root node, and to provide a resolution service to a corresponding client. Using the present invention enhances the security and stability of DNS resolution.