Mesh network supported by IEEE802.16-2004 wireless-MAN standard is a fresh network combining tree network and ad hoc network. Aimed at the weakness both in security and efficiency of one-hop one-way authentication SA (security association) mechanism employed by Mesh network, an multi-hops mutual authentication SA mechanism associated with hypo- optimal self-modified routing is proposed. Compared with the one-hop one-way mechanism, this one is of forward security and immune to middle attacks, which also lessens system cost and time delay in transmission. The employment of self-modified routing before touting establishment in management information transaction can also reduce the delay of service-flow creation. Subsequently, the security of multi-hops mutual mechanism is proved by security analysis, followed by the efficiency comparison which introduces the efficiency advantage of this mechanism.