Abstract: The paper is dealing with the IPSec Protocols and analysing the structure and key technology of security association, authentication header, encapsulating security payload and Internet key exchange. On the basis of the discussion, it presents the practical design of IPSec, which can effectively ensure the security of data transmission in IPv6. In practice, there are two models can be selected, transmission model and tunnel model, transmission model can only be used on condition that IPSec is applied to the systems of the sender and the receiver. Therefore, in most cases, tunnel model is used because it is not necessary to make any change to the user's system.