In BGP/MPLS VPNs, Border Gateway Protocol (BGP) is used to exchange Virtual Private Network (VPN) routing information throughout the provider network consisting of Autonomous Systems (ASes). Configuration errors in BGP/MPLS VPNs can increase Autonomous Systems Border Routers (ASBRs) or Provider Edge (PE) routers overhead on memory and CPU, and even lead to the failure of VPN services. This paper presents an approach that can detect BGP configuration errors based on prefixes sets of neighboring ASes and the AS relationships. This approach requires that every ASBR or PE router respectively remains a prefixes set of each trusted AS and an AS relationships set constructed according bilateral economical agreements. Simulation shows that our solution can effectively detect original misconfigurations and export misconfigurations.