In Virtual Private Networks（VPN）

security is a performance that the users are most concerned about.This paper analyzes the security guarantee mechanism for Multi-Protocol Label Switching（MPLS） VPN and the possible security risks that the core networks may encounter.On this basis

it proposes an improved program and verifies it in experiments.In the core networks

Message-Digest algorithm 5（MD5） is adopted among Border Gateway Protocol（BGP） neighbors and the Generalized TTL Security Mechanism（GTSM） for the Label Distribution Protocol（LDP） neighbors.Taking security and complexity both into consideration

this program is proved to be effective in enhancing the security of MPLS VPN core networks.