IPv4 and IPv6 will coexist for a long time, due to ISPes’ inertia in the transition from IPv4 to IPv6. Domain Name System (DNS) is a very important functional unit in the Internet. This paper describres the hierarchy and operating process of IPv6 DNS, IPv6 DNS resolver, and presents the DNS transition from IPv4 to IPv6 in particular. We suggest two methods to implement DNS service during the transition period: DNS-Application Level Gateway (DNS-ALG) with Network Address Translation-Protocol Translation (NAT-PT), and dual stacks. And we also propose their respective operational principles. This paper is of valuable reference for network engineers to construct DNS in the transition phase.