Network virtualization technology has attracted many attentions since it was proposed to provide a method to solve the ossification of Internet structure. On the platform of virtual routers, many servers connect with each other as a physical network. Mapping physical network resources to virtual network devices through the virtual network mapping technology can form many virtual networks and meet various needs of users. The resource allocation of virtual routers is a fundamental issue of network virtualization. The utilization rate of virtual network resources and the performance of the system are largely defined by the mapping method between virtual routers instances and physical resources. Aiming at the problem of resource allocation in the virtual router system, we design a physical network resource model and a virtual router resource quest model. We also propose a heuristic algorithm to solve the resource allocation problem, and then analyze the complexity of the algorithm and the utilization of physical resources.