IPv6-to-IPv6 network address translation provides a new mapping mechanism to design a NAT in IPv6. In order to solve the translation problem of IPv6 addresses with different length prefixes, a new IPv6-to-IPv6 Network Address Translation method is proposed in this paper, which is called Partial-state Asymmetric NAT (PANAT). With PANAT, it is able to provide application independent translation methods and keeps the Checksum-Neutral at the transport layer. This method can be adopted in transition technology, multi-homing, topology hiding and so on. It is implemented by modifying Linux kernel and the experimental results show that this method provides end-to-end reachability at the network layer and keeps the Checksum-Neutral at the transport layer.