Abstract: In this paper, we analyze the problem that we must implement the interconnection of IPv4 and IPv6 network while decrease the consumption of the IPv4 addresses when we employed IPv6 on Backbone. Then, based on the comparison of several issues of IPv4/IPv6 transition, we provided a suggestion that we can integrate a NAPT-PT system in the gateway on the edge of IPv4 and IPv6 net. Additionally, we introduced the shortcoming of the NAPT-PT system on the MAN and the key to them in the realization.