Abstract: The current resource scheduling algorithms can not offer promise for the fairness of shared resources based on research on the resource scheduling algorithms in the system virtualization tools represented by Xen. This paper proposes a Historical Forwarding Overhead Based the Resource Scheduling Algorithm (HFOB_RSA) to ensure that router instances occupy determinate physical resources including I/Os that should be proportional to actual requirements. This algorithm can determine the scheduling priority of router instances by calculating the last several forwarding overhead of each router instance to make those router instances with low real throughput have an opportunity for being scheduled. Meanwhile, this algorithm also sets the value of processing delay in priority formula to provide support for those delay-sensitive router instances and determines whether or not to discard the non-disposed packets in advance by forecasting their processing time to avoid the unwanted overhead. The experimental results prove that the HFOB_RSA has superiority over Credit algorithm in terms of the fairness of shared resources in the virtual router. And HFOB_RSA also is able to provide support for the delay-sensitive router instances.