Abstract: The disadvantages of traditional VPN (virtual private network) and the advantages of MPLS L2 VPN(layer 2 VPN based on multiple protocol label switch) were discussed.Data forwarding and the control are the two probelems to be solved to implement L2 VPN based on MPLS.The key technologies to implement MPLS L2 VPN consist of fowarding the L2 frames of VPN users,establishment of VC_FTN(forwarding equivalance class to NHLFE map) table based on VC(virtual circuit) information,and design of upper and lower state machines of VC between PEs using LSP(label switch path) tunnel.