Abstract: Virtual network service persistence will be impacted by substrate node or link failure, so how to achieve the reliable mapping of virtual network is recently an important problem to be solved. In this paper, a virtual network mapping problem is modeled, and then the reliability of virtual network is quantified and analyzed to sum up the main influence factors. To overcome these factors, an algorithm of Virtual Network Mapping based on Topology Impact Degree (VNM-TID) and a Migration Algorithm based on Backtracking (MA-Back) are separately proposed. Simulation results show that the algorithms have advantages on virtual network Request Accepted Ratio (RAR), Migration Success Ratio (MSR) and Valid Loading Ratio (VLR), and therefore improve the reliability of virtual network.