A trusted network access controlling method based upon tri-element peer authentication comprises: Firstly initializing creditability collectors and a creditability verifier; then carrying out a tri-element peer authentication protocol among a network access requester, a network access controller and an authentication strategy server in a network access control layer to realize bi-directional user authentication between the access requester and the access controller; When authentication is successful or the locale strategy requires to carry out a when a platform creditability evaluation process, the TNC terminal, TNC server and evaluation strategy server in a trusted platform evaluation layer performing the tri-element peer authentication protocol to realize bi-directional platform creditability authentication between the access requester and the access controller; Finally the access requester and the access controller controlling ports according to the recommendation generated by the TNAC client terminal and the TNAC service terminal. The invention solves the technical problem about poor expandability in background, and further solves the problem about complex key negotiation and relatively low safety.